diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7362e4b4e7ed5..032ca6caea465 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Add pointer based lag metric in pull-based ingestion ([#19635](https://github.com/opensearch-project/OpenSearch/pull/19635))
 - Introduced internal API for retrieving metadata about requested indices from transport actions  ([#18523](https://github.com/opensearch-project/OpenSearch/pull/18523))
 - Add cluster defaults for merge autoThrottle, maxMergeThreads, and maxMergeCount; Add segment size filter to the merged segment warmer ([#19629](https://github.com/opensearch-project/OpenSearch/pull/19629))
+- Add SMILE/CBOR/YAML document format support to Bulk GRPC endpoint ([#19744](https://github.com/opensearch-project/OpenSearch/pull/19744))
 
 ### Changed
 - Faster `terms` query creation for `keyword` field with index and docValues enabled ([#19350](https://github.com/opensearch-project/OpenSearch/pull/19350))
diff --git a/modules/transport-grpc/src/main/java/org/opensearch/transport/grpc/proto/request/document/bulk/BulkRequestParserProtoUtils.java b/modules/transport-grpc/src/main/java/org/opensearch/transport/grpc/proto/request/document/bulk/BulkRequestParserProtoUtils.java
index af48f4602b56c..f02a9bbd2238b 100644
--- a/modules/transport-grpc/src/main/java/org/opensearch/transport/grpc/proto/request/document/bulk/BulkRequestParserProtoUtils.java
+++ b/modules/transport-grpc/src/main/java/org/opensearch/transport/grpc/proto/request/document/bulk/BulkRequestParserProtoUtils.java
@@ -82,6 +82,21 @@ private static Boolean valueOrDefault(Boolean value, Boolean globalDefault) {
         return value;
     }
 
+    /**
+     * Detects the media type from the byte content, with fallback to JSON if detection fails.
+     * This enables support for JSON, SMILE, and CBOR formats in gRPC bulk requests.
+     *
+     * @param document The document content as bytes
+     * @return The detected MediaType, or JSON if detection fails or document is empty
+     */
+    static MediaType detectMediaType(byte[] document) {
+        if (document == null || document.length == 0) {
+            return MediaTypeRegistry.JSON;
+        }
+        MediaType detectedType = MediaTypeRegistry.mediaTypeFromBytes(document, 0, document.length);
+        return detectedType != null ? detectedType : MediaTypeRegistry.JSON;
+    }
+
     /**
      * Similar to {@link BulkRequestParser#parse(BytesReference, String, String, FetchSourceContext, String, Boolean, boolean, MediaType, Consumer, Consumer, Consumer)}, except that it takes into account global values.
      *
@@ -231,6 +246,7 @@ public static IndexRequest buildCreateRequest(
         pipeline = createOperation.hasPipeline() ? createOperation.getPipeline() : pipeline;
         requireAlias = createOperation.hasRequireAlias() ? createOperation.getRequireAlias() : requireAlias;
 
+        MediaType mediaType = detectMediaType(document);
         IndexRequest indexRequest = new IndexRequest(index).id(id)
             .routing(routing)
             .version(version)
@@ -239,7 +255,7 @@ public static IndexRequest buildCreateRequest(
             .setPipeline(pipeline)
             .setIfSeqNo(ifSeqNo)
             .setIfPrimaryTerm(ifPrimaryTerm)
-            .source(document, MediaTypeRegistry.JSON)
+            .source(document, mediaType)
             .setRequireAlias(requireAlias);
         return indexRequest;
     }
@@ -288,6 +304,7 @@ public static IndexRequest buildIndexRequest(
         ifPrimaryTerm = indexOperation.hasIfPrimaryTerm() ? indexOperation.getIfPrimaryTerm() : ifPrimaryTerm;
         requireAlias = indexOperation.hasRequireAlias() ? indexOperation.getRequireAlias() : requireAlias;
 
+        MediaType mediaType = detectMediaType(document);
         IndexRequest indexRequest;
         if (opType == null) {
             indexRequest = new IndexRequest(index).id(id)
@@ -297,7 +314,7 @@ public static IndexRequest buildIndexRequest(
                 .setPipeline(pipeline)
                 .setIfSeqNo(ifSeqNo)
                 .setIfPrimaryTerm(ifPrimaryTerm)
-                .source(document, MediaTypeRegistry.JSON)
+                .source(document, mediaType)
                 .setRequireAlias(requireAlias);
         } else {
             indexRequest = new IndexRequest(index).id(id)
@@ -308,7 +325,7 @@ public static IndexRequest buildIndexRequest(
                 .setPipeline(pipeline)
                 .setIfSeqNo(ifSeqNo)
                 .setIfPrimaryTerm(ifPrimaryTerm)
-                .source(document, MediaTypeRegistry.JSON)
+                .source(document, mediaType)
                 .setRequireAlias(requireAlias);
         }
         return indexRequest;
@@ -408,7 +425,9 @@ public static UpdateRequest fromProto(
             }
 
             if (updateAction.hasUpsert()) {
-                updateRequest.upsert(updateAction.getUpsert(), MediaTypeRegistry.JSON);
+                byte[] upsertBytes = updateAction.getUpsert().toByteArray();
+                MediaType upsertMediaType = detectMediaType(upsertBytes);
+                updateRequest.upsert(upsertBytes, upsertMediaType);
             }
 
             if (updateAction.hasDocAsUpsert()) {
@@ -424,7 +443,8 @@ public static UpdateRequest fromProto(
             }
         }
 
-        updateRequest.doc(document, MediaTypeRegistry.JSON);
+        MediaType mediaType = detectMediaType(document);
+        updateRequest.doc(document, mediaType);
 
         if (updateOperation.hasIfSeqNo()) {
             updateRequest.setIfSeqNo(updateOperation.getIfSeqNo());
diff --git a/modules/transport-grpc/src/test/java/org/opensearch/transport/grpc/proto/request/document/bulk/BulkRequestParserProtoUtilsTests.java b/modules/transport-grpc/src/test/java/org/opensearch/transport/grpc/proto/request/document/bulk/BulkRequestParserProtoUtilsTests.java
index 2141479642c13..81fd666dbc980 100644
--- a/modules/transport-grpc/src/test/java/org/opensearch/transport/grpc/proto/request/document/bulk/BulkRequestParserProtoUtilsTests.java
+++ b/modules/transport-grpc/src/test/java/org/opensearch/transport/grpc/proto/request/document/bulk/BulkRequestParserProtoUtilsTests.java
@@ -14,6 +14,7 @@
 import org.opensearch.action.index.IndexRequest;
 import org.opensearch.action.update.UpdateRequest;
 import org.opensearch.common.lucene.uid.Versions;
+import org.opensearch.core.xcontent.MediaType;
 import org.opensearch.index.VersionType;
 import org.opensearch.index.seqno.SequenceNumbers;
 import org.opensearch.protobufs.BulkRequest;
@@ -716,4 +717,325 @@ public void testFromProtoWithAllUpdateActionFields() {
         assertEquals("IfSeqNo should be set", 123L, result.ifSeqNo());
         assertEquals("IfPrimaryTerm should be set", 456L, result.ifPrimaryTerm());
     }
+
+    public void testBuildCreateRequestWithSmileContent() throws Exception {
+        WriteOperation writeOperation = WriteOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        // Create SMILE-encoded document
+        byte[] smileDocument = createSmileDocument();
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildCreateRequest(
+            writeOperation,
+            smileDocument,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertEquals("Index should match", "test-index", indexRequest.index());
+        assertEquals("Id should match", "test-id", indexRequest.id());
+        assertNotNull("Source should be set", indexRequest.source());
+        // Verify the content type was detected as SMILE
+        assertEquals("Content type should be SMILE", "application/smile", indexRequest.getContentType().mediaType());
+    }
+
+    public void testBuildCreateRequestWithCborContent() throws Exception {
+        WriteOperation writeOperation = WriteOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        // Create CBOR-encoded document
+        byte[] cborDocument = createCborDocument();
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildCreateRequest(
+            writeOperation,
+            cborDocument,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertEquals("Index should match", "test-index", indexRequest.index());
+        assertEquals("Id should match", "test-id", indexRequest.id());
+        assertNotNull("Source should be set", indexRequest.source());
+        // Verify the content type was detected as CBOR
+        assertEquals("Content type should be CBOR", "application/cbor", indexRequest.getContentType().mediaType());
+    }
+
+    public void testBuildIndexRequestWithSmileContent() throws Exception {
+        IndexOperation indexOperation = IndexOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        // Create SMILE-encoded document
+        byte[] smileDocument = createSmileDocument();
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildIndexRequest(
+            indexOperation,
+            smileDocument,
+            null,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertEquals("Index should match", "test-index", indexRequest.index());
+        assertNotNull("Source should be set", indexRequest.source());
+        // Verify the content type was detected as SMILE
+        assertEquals("Content type should be SMILE", "application/smile", indexRequest.getContentType().mediaType());
+    }
+
+    public void testBuildIndexRequestWithCborContent() throws Exception {
+        IndexOperation indexOperation = IndexOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        // Create CBOR-encoded document
+        byte[] cborDocument = createCborDocument();
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildIndexRequest(
+            indexOperation,
+            cborDocument,
+            null,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertEquals("Index should match", "test-index", indexRequest.index());
+        assertNotNull("Source should be set", indexRequest.source());
+        // Verify the content type was detected as CBOR
+        assertEquals("Content type should be CBOR", "application/cbor", indexRequest.getContentType().mediaType());
+    }
+
+    public void testUpdateRequestWithCborUpsert() throws Exception {
+        UpdateRequest updateRequest = new UpdateRequest("test-index", "test-id");
+        byte[] document = "{\"field\":\"value\"}".getBytes(StandardCharsets.UTF_8);
+
+        // Create CBOR-encoded upsert document
+        byte[] cborUpsert = createCborDocument();
+
+        BulkRequestBody bulkRequestBody = BulkRequestBody.newBuilder()
+            .setUpdateAction(org.opensearch.protobufs.UpdateAction.newBuilder().setUpsert(ByteString.copyFrom(cborUpsert)).build())
+            .build();
+
+        UpdateOperation updateOperation = UpdateOperation.newBuilder().build();
+
+        UpdateRequest result = BulkRequestParserProtoUtils.fromProto(updateRequest, document, bulkRequestBody, updateOperation);
+
+        assertNotNull("Result should not be null", result);
+        assertNotNull("Upsert should be set", result.upsertRequest());
+    }
+
+    public void testBuildCreateRequestWithEmptyDocument() {
+        WriteOperation writeOperation = WriteOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        byte[] emptyDocument = new byte[0];
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildCreateRequest(
+            writeOperation,
+            emptyDocument,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertNotNull("Source should be set", indexRequest.source());
+        // Empty document should default to JSON
+        assertTrue("Content type should default to JSON", indexRequest.getContentType().mediaType().startsWith("application/json"));
+    }
+
+    public void testBuildCreateRequestWithJsonContent() throws Exception {
+        WriteOperation writeOperation = WriteOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        // Create JSON document
+        byte[] jsonDocument = "{\"field\":\"value\"}".getBytes(StandardCharsets.UTF_8);
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildCreateRequest(
+            writeOperation,
+            jsonDocument,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertEquals("Index should match", "test-index", indexRequest.index());
+        assertEquals("Id should match", "test-id", indexRequest.id());
+        assertNotNull("Source should be set", indexRequest.source());
+        // Verify the content type was detected as JSON (may include charset)
+        assertTrue("Content type should be JSON", indexRequest.getContentType().mediaType().startsWith("application/json"));
+    }
+
+    public void testBuildCreateRequestWithYamlContent() throws Exception {
+        WriteOperation writeOperation = WriteOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        // Create YAML-encoded document
+        byte[] yamlDocument = createYamlDocument();
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildCreateRequest(
+            writeOperation,
+            yamlDocument,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertEquals("Index should match", "test-index", indexRequest.index());
+        assertEquals("Id should match", "test-id", indexRequest.id());
+        assertNotNull("Source should be set", indexRequest.source());
+        // Verify the content type was detected as YAML
+        assertEquals("Content type should be YAML", "application/yaml", indexRequest.getContentType().mediaType());
+    }
+
+    public void testBuildIndexRequestWithJsonContent() throws Exception {
+        IndexOperation indexOperation = IndexOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        // Create JSON document
+        byte[] jsonDocument = "{\"field\":\"value\"}".getBytes(StandardCharsets.UTF_8);
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildIndexRequest(
+            indexOperation,
+            jsonDocument,
+            null,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertEquals("Index should match", "test-index", indexRequest.index());
+        assertNotNull("Source should be set", indexRequest.source());
+        // Verify the content type was detected as JSON (may include charset)
+        assertTrue("Content type should be JSON", indexRequest.getContentType().mediaType().startsWith("application/json"));
+    }
+
+    public void testBuildIndexRequestWithYamlContent() throws Exception {
+        IndexOperation indexOperation = IndexOperation.newBuilder().setXIndex("test-index").setXId("test-id").build();
+
+        // Create YAML-encoded document
+        byte[] yamlDocument = createYamlDocument();
+
+        IndexRequest indexRequest = BulkRequestParserProtoUtils.buildIndexRequest(
+            indexOperation,
+            yamlDocument,
+            null,
+            "default-index",
+            "default-id",
+            null,
+            Versions.MATCH_ANY,
+            VersionType.INTERNAL,
+            null,
+            SequenceNumbers.UNASSIGNED_SEQ_NO,
+            UNASSIGNED_PRIMARY_TERM,
+            false
+        );
+
+        assertNotNull("IndexRequest should not be null", indexRequest);
+        assertEquals("Index should match", "test-index", indexRequest.index());
+        assertNotNull("Source should be set", indexRequest.source());
+        // Verify the content type was detected as YAML
+        assertEquals("Content type should be YAML", "application/yaml", indexRequest.getContentType().mediaType());
+    }
+
+    /**
+     * Helper method to create a SMILE-encoded document.
+     */
+    private byte[] createSmileDocument() throws Exception {
+        org.opensearch.core.xcontent.XContentBuilder builder = org.opensearch.common.xcontent.XContentFactory.smileBuilder();
+        builder.startObject();
+        builder.field("field", "value");
+        builder.endObject();
+        return org.opensearch.core.common.bytes.BytesReference.toBytes(org.opensearch.core.common.bytes.BytesReference.bytes(builder));
+    }
+
+    /**
+     * Helper method to create a CBOR-encoded document.
+     */
+    private byte[] createCborDocument() throws Exception {
+        org.opensearch.core.xcontent.XContentBuilder builder = org.opensearch.common.xcontent.XContentFactory.cborBuilder();
+        builder.startObject();
+        builder.field("field", "value");
+        builder.endObject();
+        return org.opensearch.core.common.bytes.BytesReference.toBytes(org.opensearch.core.common.bytes.BytesReference.bytes(builder));
+    }
+
+    /**
+     * Helper method to create a YAML-encoded document.
+     */
+    private byte[] createYamlDocument() throws Exception {
+        org.opensearch.core.xcontent.XContentBuilder builder = org.opensearch.common.xcontent.XContentFactory.yamlBuilder();
+        builder.startObject();
+        builder.field("field", "value");
+        builder.endObject();
+        return org.opensearch.core.common.bytes.BytesReference.toBytes(org.opensearch.core.common.bytes.BytesReference.bytes(builder));
+    }
+
+    /**
+     * Test detectMediaType with null or empty document
+     */
+    public void testDetectMediaTypeNullOrEmpty() {
+        MediaType result = BulkRequestParserProtoUtils.detectMediaType(null);
+        assertEquals("application/json", result.mediaTypeWithoutParameters());
+
+        result = BulkRequestParserProtoUtils.detectMediaType(new byte[0]);
+        assertEquals("application/json", result.mediaTypeWithoutParameters());
+    }
+
+    /**
+     * Test detectMediaType with unrecognizable format
+     */
+    public void testDetectMediaTypeUnrecognizable() {
+        byte[] invalidBytes = new byte[] { (byte) 0xFF, (byte) 0xFE, (byte) 0xFD, (byte) 0xFC };
+        MediaType result = BulkRequestParserProtoUtils.detectMediaType(invalidBytes);
+        assertEquals("application/json", result.mediaTypeWithoutParameters());
+    }
 }