diff --git a/integration-tests/src/main/java/org/apache/polaris/service/it/test/PolarisPolicyServiceIntegrationTest.java b/integration-tests/src/main/java/org/apache/polaris/service/it/test/PolarisPolicyServiceIntegrationTest.java
index c610f13ffa..c836ffdabc 100644
--- a/integration-tests/src/main/java/org/apache/polaris/service/it/test/PolarisPolicyServiceIntegrationTest.java
+++ b/integration-tests/src/main/java/org/apache/polaris/service/it/test/PolarisPolicyServiceIntegrationTest.java
@@ -73,10 +73,13 @@
 import org.apache.polaris.service.it.env.PolicyApi;
 import org.apache.polaris.service.it.ext.PolarisIntegrationTestExtension;
 import org.apache.polaris.service.types.ApplicablePolicy;
+import org.apache.polaris.service.types.AttachPolicyRequest;
 import org.apache.polaris.service.types.CreatePolicyRequest;
+import org.apache.polaris.service.types.DetachPolicyRequest;
 import org.apache.polaris.service.types.Policy;
 import org.apache.polaris.service.types.PolicyAttachmentTarget;
 import org.apache.polaris.service.types.PolicyIdentifier;
+import org.apache.polaris.service.types.UpdatePolicyRequest;
 import org.assertj.core.api.Assertions;
 import org.assertj.core.api.InstanceOfAssertFactories;
 import org.junit.jupiter.api.AfterAll;
@@ -107,6 +110,13 @@ public class PolarisPolicyServiceIntegrationTest {
   private static final PolicyIdentifier NS1_P3 = new PolicyIdentifier(NS1, "P3");
   private static final TableIdentifier NS2_T1 = TableIdentifier.of(NS2, "T1");
 
+  private static final String NS1_NAME = RESTUtil.encodeNamespace(NS1);
+  private static final String INVALID_NAMESPACE = "INVALID_NAMESPACE";
+  private static final String INVALID_POLICY = "INVALID_POLICY";
+  private static final String INVALID_TABLE = "INVALID_TABLE";
+  private static final String INVALID_NAMESPACE_MSG =
+      "Namespace does not exist: " + INVALID_NAMESPACE;
+
   private static URI s3BucketBase;
   private static String principalRoleName;
   private static ClientCredentials adminCredentials;
@@ -333,6 +343,141 @@ public void testCreatePolicyWithInvalidName(String policyName) {
     }
   }
 
+  @Test
+  public void testCreatePolicyWithNonExistingNamespace() {
+    CreatePolicyRequest request =
+        CreatePolicyRequest.builder()
+            .setType(PredefinedPolicyTypes.DATA_COMPACTION.getName())
+            .setName(currentCatalogName)
+            .setDescription("test policy")
+            .setContent(EXAMPLE_TABLE_MAINTENANCE_POLICY_CONTENT)
+            .build();
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies",
+                Map.of("cat", currentCatalogName, "ns", INVALID_NAMESPACE))
+            .post(Entity.json(request))) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class)).contains(INVALID_NAMESPACE_MSG);
+    }
+  }
+
+  @Test
+  public void testAttachPolicyToNonExistingNamespace() {
+    restCatalog.createNamespace(NS1);
+    policyApi.createPolicy(
+        currentCatalogName,
+        NS1_P1,
+        PredefinedPolicyTypes.DATA_COMPACTION,
+        EXAMPLE_TABLE_MAINTENANCE_POLICY_CONTENT,
+        "test policy");
+
+    Namespace invalidNamespace = Namespace.of(INVALID_NAMESPACE);
+    var invalidTarget =
+        new PolicyAttachmentTarget(
+            PolicyAttachmentTarget.TypeEnum.NAMESPACE, List.of(invalidNamespace.levels()));
+
+    AttachPolicyRequest request =
+        AttachPolicyRequest.builder().setTarget(invalidTarget).setParameters(Map.of()).build();
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies/{policy-name}/mappings",
+                Map.of("cat", currentCatalogName, "ns", NS1_NAME, "policy-name", NS1_P1.getName()))
+            .put(Entity.json(request))) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class)).contains(INVALID_NAMESPACE_MSG);
+    }
+    policyApi.dropPolicy(currentCatalogName, NS1_P1);
+  }
+
+  @Test
+  public void testAttachPolicyToNonExistingTable() {
+    restCatalog.createNamespace(NS1);
+    policyApi.createPolicy(
+        currentCatalogName,
+        NS1_P1,
+        PredefinedPolicyTypes.DATA_COMPACTION,
+        EXAMPLE_TABLE_MAINTENANCE_POLICY_CONTENT,
+        "test policy");
+    TableIdentifier invalidTable = TableIdentifier.of(NS1, INVALID_TABLE);
+    var invalidTarget =
+        new PolicyAttachmentTarget(
+            PolicyAttachmentTarget.TypeEnum.TABLE_LIKE,
+            List.of(invalidTable.toString().split("\\.")));
+
+    AttachPolicyRequest request =
+        AttachPolicyRequest.builder().setTarget(invalidTarget).setParameters(Map.of()).build();
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies/{policy-name}/mappings",
+                Map.of("cat", currentCatalogName, "ns", NS1_NAME, "policy-name", NS1_P1.getName()))
+            .put(Entity.json(request))) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class))
+          .contains("Table or view does not exist: " + NS1_NAME + "." + INVALID_TABLE);
+    }
+    policyApi.dropPolicy(currentCatalogName, NS1_P1);
+  }
+
+  @Test
+  public void testDetachPolicyFromNonExistingNamespace() {
+    restCatalog.createNamespace(NS1);
+    policyApi.createPolicy(
+        currentCatalogName,
+        NS1_P1,
+        PredefinedPolicyTypes.DATA_COMPACTION,
+        EXAMPLE_TABLE_MAINTENANCE_POLICY_CONTENT,
+        "test policy");
+    Namespace invalidNamespace = Namespace.of(INVALID_NAMESPACE);
+    var invalidTarget =
+        new PolicyAttachmentTarget(
+            PolicyAttachmentTarget.TypeEnum.NAMESPACE, List.of(invalidNamespace.levels()));
+
+    DetachPolicyRequest request = DetachPolicyRequest.builder().setTarget(invalidTarget).build();
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies/{policy-name}/mappings",
+                Map.of("cat", currentCatalogName, "ns", NS1_NAME, "policy-name", NS1_P1.getName()))
+            .post(Entity.json(request))) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class)).contains(INVALID_NAMESPACE_MSG);
+    }
+    policyApi.dropPolicy(currentCatalogName, NS1_P1);
+  }
+
+  @Test
+  public void testDetachPolicyFromNonExistingTable() {
+    restCatalog.createNamespace(NS1);
+    policyApi.createPolicy(
+        currentCatalogName,
+        NS1_P1,
+        PredefinedPolicyTypes.DATA_COMPACTION,
+        EXAMPLE_TABLE_MAINTENANCE_POLICY_CONTENT,
+        "test policy");
+    TableIdentifier invalidTable = TableIdentifier.of(NS1, INVALID_TABLE);
+    var invalidTarget =
+        new PolicyAttachmentTarget(
+            PolicyAttachmentTarget.TypeEnum.TABLE_LIKE,
+            List.of(invalidTable.toString().split("\\.")));
+
+    DetachPolicyRequest request = DetachPolicyRequest.builder().setTarget(invalidTarget).build();
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies/{policy-name}/mappings",
+                Map.of("cat", currentCatalogName, "ns", NS1_NAME, "policy-name", NS1_P1.getName()))
+            .post(Entity.json(request))) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class))
+          .contains("Table or view does not exist: " + NS1_NAME + "." + INVALID_TABLE);
+    }
+    policyApi.dropPolicy(currentCatalogName, NS1_P1);
+  }
+
   @Test
   public void testDropPolicy() {
     restCatalog.createNamespace(NS1);
@@ -359,6 +504,24 @@ public void testDropPolicy() {
         .hasSize(0);
   }
 
+  @Test
+  public void testDropNonExistingPolicy() {
+    restCatalog.createNamespace(NS1);
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies/{policy}",
+                Map.of("cat", currentCatalogName, "ns", NS1_NAME, "policy", INVALID_POLICY))
+            .delete()) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class))
+          .contains(
+              "Policy does not exist: class PolicyIdentifier",
+              "namespace: " + NS1_NAME,
+              "name: " + INVALID_POLICY);
+    }
+  }
+
   @Test
   public void testUpdatePolicy() {
     restCatalog.createNamespace(NS1);
@@ -387,6 +550,29 @@ public void testUpdatePolicy() {
     policyApi.dropPolicy(currentCatalogName, NS1_P1);
   }
 
+  @Test
+  public void testUpdateNonExistingPolicy() {
+    restCatalog.createNamespace(NS1);
+    UpdatePolicyRequest request =
+        UpdatePolicyRequest.builder()
+            .setContent("{\"enable\":false}")
+            .setDescription("updated test policy")
+            .build();
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies/{policy}",
+                Map.of("cat", currentCatalogName, "ns", NS1_NAME, "policy", INVALID_POLICY))
+            .put(Entity.json(request))) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class))
+          .contains(
+              "Policy does not exist: class PolicyIdentifier",
+              "namespace: " + NS1_NAME,
+              "name: " + INVALID_POLICY);
+    }
+  }
+
   @Test
   public void testListPolicies() {
     restCatalog.createNamespace(NS1);
@@ -417,6 +603,74 @@ public void testListPolicies() {
     policyApi.dropPolicy(currentCatalogName, NS1_P2);
   }
 
+  @Test
+  public void testListPoliciesOnNonExistingNamespace() {
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies",
+                Map.of("cat", currentCatalogName, "ns", INVALID_NAMESPACE))
+            .get()) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class)).contains(INVALID_NAMESPACE_MSG);
+    }
+  }
+
+  @Test
+  public void testGetApplicablePoliciesOnNonExistingNamespace() {
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/applicable-policies",
+                Map.of("cat", currentCatalogName),
+                Map.of("namespace", INVALID_NAMESPACE))
+            .get()) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class)).contains(INVALID_NAMESPACE_MSG);
+    }
+  }
+
+  @Test
+  public void testGetApplicablePoliciesOnNonExistingTable() {
+    restCatalog.createNamespace(NS1);
+    policyApi.createPolicy(
+        currentCatalogName,
+        NS1_P1,
+        PredefinedPolicyTypes.DATA_COMPACTION,
+        EXAMPLE_TABLE_MAINTENANCE_POLICY_CONTENT,
+        "test policy");
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/applicable-policies",
+                Map.of("cat", currentCatalogName),
+                Map.of("namespace", NS1_NAME, "target-name", INVALID_TABLE))
+            .get()) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class))
+          .contains("Table does not exist: " + NS1_NAME + "." + INVALID_TABLE);
+    }
+    policyApi.dropPolicy(currentCatalogName, NS1_P1);
+  }
+
+  @Test
+  public void testLoadNonExistingPolicy() {
+    restCatalog.createNamespace(NS1);
+    try (Response res =
+        policyApi
+            .request(
+                "polaris/v1/{cat}/namespaces/{ns}/policies/{policy}",
+                Map.of("cat", currentCatalogName, "ns", NS1_NAME, "policy", INVALID_POLICY))
+            .get()) {
+      Assertions.assertThat(res.getStatus()).isEqualTo(Response.Status.NOT_FOUND.getStatusCode());
+      Assertions.assertThat(res.readEntity(String.class))
+          .contains(
+              "Policy does not exist: class PolicyIdentifier",
+              "namespace: " + NS1_NAME,
+              "name: " + INVALID_POLICY);
+    }
+  }
+
   @Test
   public void testPolicyMapping() {
     restCatalog.createNamespace(NS1);