diff --git a/CHANGELOG.md b/CHANGELOG.md
index 51817010ccfcb..b460bb8e344ea 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -48,6 +48,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Refactor the RemoteTranslogTransferTracker.Stats and RemoteSegmentTransferTracker.Stats class to use the Builder pattern instead of constructors ([#19837](https://github.com/opensearch-project/OpenSearch/pull/19837))
 - Refactor the GetStats, FlushStats and QueryCacheStats class to use the Builder pattern instead of constructors ([#19935](https://github.com/opensearch-project/OpenSearch/pull/19935))
 - Add RangeSemver for `dependencies` in `plugin-descriptor.properties` ([#19939](https://github.com/opensearch-project/OpenSearch/pull/19939))
+- Refactor the FieldDataStats and CompletionStats class to use the Builder pattern instead of constructors ([#19936](https://github.com/opensearch-project/OpenSearch/pull/19936))
 
 ### Fixed
 - Fix Allocation and Rebalance Constraints of WeightFunction are incorrectly reset ([#19012](https://github.com/opensearch-project/OpenSearch/pull/19012))
@@ -101,6 +102,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Deprecated existing constructors in Condition.Stats and DirectoryFileTransferTracker.Stats in favor of the new Builder ([#19862](https://github.com/opensearch-project/OpenSearch/pull/19862))
 - Deprecated existing constructors in RemoteTranslogTransferTracker.Stats and RemoteSegmentTransferTracker.Stats in favor of the new Builder ([#19837](https://github.com/opensearch-project/OpenSearch/pull/19837))
 - Deprecated existing constructors in GetStats, FlushStats and QueryCacheStats in favor of the new Builder ([#19935](https://github.com/opensearch-project/OpenSearch/pull/19935))
+- Deprecated existing constructors in FieldDataStats and CompletionStats in favor of the new Builder ([#19936](https://github.com/opensearch-project/OpenSearch/pull/19936))
 
 ### Removed
 
diff --git a/server/src/main/java/org/opensearch/index/engine/CompletionStatsCache.java b/server/src/main/java/org/opensearch/index/engine/CompletionStatsCache.java
index 07f988d65cf76..9358325690ab4 100644
--- a/server/src/main/java/org/opensearch/index/engine/CompletionStatsCache.java
+++ b/server/src/main/java/org/opensearch/index/engine/CompletionStatsCache.java
@@ -116,7 +116,7 @@ CompletionStats get(String... fieldNamePatterns) {
                 }
             }
 
-            return new CompletionStats(sizeInBytes, new FieldMemoryStats(completionFields));
+            return new CompletionStats.Builder().sizeInBytes(sizeInBytes).fieldMemoryStats(new FieldMemoryStats(completionFields)).build();
         });
 
         boolean success = false;
@@ -153,7 +153,7 @@ private static CompletionStats filterCompletionStatsByFieldName(String[] fieldNa
         } else {
             fieldMemoryStats = null;
         }
-        return new CompletionStats(fullCompletionStats.getSizeInBytes(), fieldMemoryStats);
+        return new CompletionStats.Builder().sizeInBytes(fullCompletionStats.getSizeInBytes()).fieldMemoryStats(fieldMemoryStats).build();
     }
 
     @Override
diff --git a/server/src/main/java/org/opensearch/index/fielddata/FieldDataStats.java b/server/src/main/java/org/opensearch/index/fielddata/FieldDataStats.java
index 1bd81c840a3d4..1251f6e2bda6f 100644
--- a/server/src/main/java/org/opensearch/index/fielddata/FieldDataStats.java
+++ b/server/src/main/java/org/opensearch/index/fielddata/FieldDataStats.java
@@ -67,12 +67,28 @@ public FieldDataStats() {
 
     }
 
+    /**
+     * Private constructor that takes a builder.
+     * This is the sole entry point for creating a new FieldDataStats object.
+     * @param builder The builder instance containing all the values.
+     */
+    private FieldDataStats(Builder builder) {
+        this.memorySize = builder.memorySize;
+        this.evictions = builder.evictions;
+        this.fields = builder.fields;
+    }
+
     public FieldDataStats(StreamInput in) throws IOException {
         memorySize = in.readVLong();
         evictions = in.readVLong();
         fields = in.readOptionalWriteable(FieldMemoryStats::new);
     }
 
+    /**
+     * This constructor will be deprecated starting in version 3.4.0.
+     * Use {@link FieldDataStats.Builder} instead.
+     */
+    @Deprecated
     public FieldDataStats(long memorySize, long evictions, @Nullable FieldMemoryStats fields) {
         this.memorySize = memorySize;
         this.evictions = evictions;
@@ -111,6 +127,41 @@ public FieldMemoryStats getFields() {
         return fields;
     }
 
+    /**
+     * Builder for the {@link FieldDataStats} class.
+     * Provides a fluent API for constructing a FieldDataStats object.
+     */
+    public static class Builder {
+        private long memorySize = 0;
+        private long evictions = 0;
+        private FieldMemoryStats fields = null;
+
+        public Builder() {}
+
+        public Builder memorySize(long memorySize) {
+            this.memorySize = memorySize;
+            return this;
+        }
+
+        public Builder evictions(long evictions) {
+            this.evictions = evictions;
+            return this;
+        }
+
+        public Builder fieldMemoryStats(@Nullable FieldMemoryStats fields) {
+            this.fields = fields;
+            return this;
+        }
+
+        /**
+         * Creates a {@link FieldDataStats} object from the builder's current state.
+         * @return A new FieldDataStats instance.
+         */
+        public FieldDataStats build() {
+            return new FieldDataStats(this);
+        }
+    }
+
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeVLong(memorySize);
diff --git a/server/src/main/java/org/opensearch/index/fielddata/ShardFieldData.java b/server/src/main/java/org/opensearch/index/fielddata/ShardFieldData.java
index d8f49ba3d9c60..2155fda870b92 100644
--- a/server/src/main/java/org/opensearch/index/fielddata/ShardFieldData.java
+++ b/server/src/main/java/org/opensearch/index/fielddata/ShardFieldData.java
@@ -67,11 +67,10 @@ public FieldDataStats stats(String... fields) {
                 }
             }
         }
-        return new FieldDataStats(
-            totalMetric.count(),
-            evictionsMetric.count(),
-            fieldTotals == null ? null : new FieldMemoryStats(fieldTotals)
-        );
+        return new FieldDataStats.Builder().memorySize(totalMetric.count())
+            .evictions(evictionsMetric.count())
+            .fieldMemoryStats(fieldTotals == null ? null : new FieldMemoryStats(fieldTotals))
+            .build();
     }
 
     @Override
diff --git a/server/src/main/java/org/opensearch/search/suggest/completion/CompletionStats.java b/server/src/main/java/org/opensearch/search/suggest/completion/CompletionStats.java
index ad91e75c591f3..993e374a82b85 100644
--- a/server/src/main/java/org/opensearch/search/suggest/completion/CompletionStats.java
+++ b/server/src/main/java/org/opensearch/search/suggest/completion/CompletionStats.java
@@ -62,11 +62,26 @@ public class CompletionStats implements Writeable, ToXContentFragment {
 
     public CompletionStats() {}
 
+    /**
+     * Private constructor that takes a builder.
+     * This is the sole entry point for creating a new CompletionStats object.
+     * @param builder The builder instance containing all the values.
+     */
+    private CompletionStats(Builder builder) {
+        this.sizeInBytes = builder.sizeInBytes;
+        this.fields = builder.fields;
+    }
+
     public CompletionStats(StreamInput in) throws IOException {
         sizeInBytes = in.readVLong();
         fields = in.readOptionalWriteable(FieldMemoryStats::new);
     }
 
+    /**
+     * This constructor will be deprecated starting in version 3.4.0.
+     * Use {@link CompletionStats.Builder} instead.
+     */
+    @Deprecated
     public CompletionStats(long size, @Nullable FieldMemoryStats fields) {
         this.sizeInBytes = size;
         this.fields = fields;
@@ -84,6 +99,35 @@ public FieldMemoryStats getFields() {
         return fields;
     }
 
+    /**
+     * Builder for the {@link CompletionStats} class.
+     * Provides a fluent API for constructing a CompletionStats object.
+     */
+    public static class Builder {
+        private long sizeInBytes = 0;
+        private FieldMemoryStats fields = null;
+
+        public Builder() {}
+
+        public Builder sizeInBytes(long bytes) {
+            this.sizeInBytes = bytes;
+            return this;
+        }
+
+        public Builder fieldMemoryStats(FieldMemoryStats fields) {
+            this.fields = fields;
+            return this;
+        }
+
+        /**
+         * Creates a {@link CompletionStats} object from the builder's current state.
+         * @return A new CompletionStats instance.
+         */
+        public CompletionStats build() {
+            return new CompletionStats(this);
+        }
+    }
+
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeVLong(sizeInBytes);
diff --git a/server/src/test/java/org/opensearch/action/admin/cluster/node/stats/NodeStatsTests.java b/server/src/test/java/org/opensearch/action/admin/cluster/node/stats/NodeStatsTests.java
index 34a041c3620db..c31c0e0349de0 100644
--- a/server/src/test/java/org/opensearch/action/admin/cluster/node/stats/NodeStatsTests.java
+++ b/server/src/test/java/org/opensearch/action/admin/cluster/node/stats/NodeStatsTests.java
@@ -1376,7 +1376,10 @@ private CommonStats createRandomCommonStats() {
             .periodic(randomLongBetween(0, 100))
             .totalTimeInMillis(randomLongBetween(0, 100))
             .build();
-        commonStats.fieldData = new FieldDataStats(randomLongBetween(0, 100), randomLongBetween(0, 100), null);
+        commonStats.fieldData = new FieldDataStats.Builder().memorySize(randomLongBetween(0, 100))
+            .evictions(randomLongBetween(0, 100))
+            .fieldMemoryStats(null)
+            .build();
         commonStats.queryCache = new QueryCacheStats.Builder().ramBytesUsed(randomLongBetween(0, 100))
             .hitCount(randomLongBetween(0, 100))
             .missCount(randomLongBetween(0, 100))
diff --git a/server/src/test/java/org/opensearch/action/admin/cluster/stats/ClusterStatsNodesTests.java b/server/src/test/java/org/opensearch/action/admin/cluster/stats/ClusterStatsNodesTests.java
index 0bbcad0407c4d..6b83fc544cbf2 100644
--- a/server/src/test/java/org/opensearch/action/admin/cluster/stats/ClusterStatsNodesTests.java
+++ b/server/src/test/java/org/opensearch/action/admin/cluster/stats/ClusterStatsNodesTests.java
@@ -375,7 +375,10 @@ private CommonStats createRandomCommonStats() {
             .periodic(randomLongBetween(0, 100))
             .totalTimeInMillis(randomLongBetween(0, 100))
             .build();
-        commonStats.fieldData = new FieldDataStats(randomLongBetween(0, 100), randomLongBetween(0, 100), null);
+        commonStats.fieldData = new FieldDataStats.Builder().memorySize(randomLongBetween(0, 100))
+            .evictions(randomLongBetween(0, 100))
+            .fieldMemoryStats(null)
+            .build();
         commonStats.queryCache = new QueryCacheStats.Builder().ramBytesUsed(randomLongBetween(0, 100))
             .hitCount(randomLongBetween(0, 100))
             .missCount(randomLongBetween(0, 100))
diff --git a/server/src/test/java/org/opensearch/action/admin/cluster/stats/ClusterStatsResponseTests.java b/server/src/test/java/org/opensearch/action/admin/cluster/stats/ClusterStatsResponseTests.java
index f673dcf56f7cd..e57ec8640b07c 100644
--- a/server/src/test/java/org/opensearch/action/admin/cluster/stats/ClusterStatsResponseTests.java
+++ b/server/src/test/java/org/opensearch/action/admin/cluster/stats/ClusterStatsResponseTests.java
@@ -243,7 +243,10 @@ private CommonStats createRandomCommonStats() {
             .periodic(randomLongBetween(0, 100))
             .totalTimeInMillis(randomLongBetween(0, 100))
             .build();
-        commonStats.fieldData = new FieldDataStats(randomLongBetween(0, 100), randomLongBetween(0, 100), null);
+        commonStats.fieldData = new FieldDataStats.Builder().memorySize(randomLongBetween(0, 100))
+            .evictions(randomLongBetween(0, 100))
+            .fieldMemoryStats(null)
+            .build();
         commonStats.queryCache = new QueryCacheStats.Builder().ramBytesUsed(randomLongBetween(0, 100))
             .hitCount(randomLongBetween(0, 100))
             .missCount(randomLongBetween(0, 100))
diff --git a/server/src/test/java/org/opensearch/index/fielddata/FieldDataStatsTests.java b/server/src/test/java/org/opensearch/index/fielddata/FieldDataStatsTests.java
index 296f760095ed1..3b16381c8189b 100644
--- a/server/src/test/java/org/opensearch/index/fielddata/FieldDataStatsTests.java
+++ b/server/src/test/java/org/opensearch/index/fielddata/FieldDataStatsTests.java
@@ -43,7 +43,10 @@ public class FieldDataStatsTests extends OpenSearchTestCase {
 
     public void testSerialize() throws IOException {
         FieldMemoryStats map = randomBoolean() ? null : FieldMemoryStatsTests.randomFieldMemoryStats();
-        FieldDataStats stats = new FieldDataStats(randomNonNegativeLong(), randomNonNegativeLong(), map);
+        FieldDataStats stats = new FieldDataStats.Builder().memorySize(randomNonNegativeLong())
+            .evictions(randomNonNegativeLong())
+            .fieldMemoryStats(map)
+            .build();
         BytesStreamOutput out = new BytesStreamOutput();
         stats.writeTo(out);
         StreamInput input = out.bytes().streamInput();
diff --git a/server/src/test/java/org/opensearch/index/suggest/stats/CompletionsStatsTests.java b/server/src/test/java/org/opensearch/index/suggest/stats/CompletionsStatsTests.java
index 104f132fb47ce..aa9137088d8e1 100644
--- a/server/src/test/java/org/opensearch/index/suggest/stats/CompletionsStatsTests.java
+++ b/server/src/test/java/org/opensearch/index/suggest/stats/CompletionsStatsTests.java
@@ -44,7 +44,7 @@ public class CompletionsStatsTests extends OpenSearchTestCase {
 
     public void testSerialize() throws IOException {
         FieldMemoryStats map = randomBoolean() ? null : FieldMemoryStatsTests.randomFieldMemoryStats();
-        CompletionStats stats = new CompletionStats(randomNonNegativeLong(), map);
+        CompletionStats stats = new CompletionStats.Builder().sizeInBytes(randomNonNegativeLong()).fieldMemoryStats(map).build();
         BytesStreamOutput out = new BytesStreamOutput();
         stats.writeTo(out);
         StreamInput input = out.bytes().streamInput();