diff --git a/java-client/src/main/java/org/opensearch/client/opensearch/_types/query_dsl/KnnQuery.java b/java-client/src/main/java/org/opensearch/client/opensearch/_types/query_dsl/KnnQuery.java
index 175fe6e11a..0c61cbd02e 100644
--- a/java-client/src/main/java/org/opensearch/client/opensearch/_types/query_dsl/KnnQuery.java
+++ b/java-client/src/main/java/org/opensearch/client/opensearch/_types/query_dsl/KnnQuery.java
@@ -8,7 +8,10 @@
 
 package org.opensearch.client.opensearch._types.query_dsl;
 
+import static java.math.RoundingMode.HALF_UP;
+
 import jakarta.json.stream.JsonGenerator;
+import java.math.BigDecimal;
 import java.util.function.Function;
 import javax.annotation.Nullable;
 import org.opensearch.client.json.JsonpDeserializable;
@@ -93,7 +96,9 @@ protected void serializeInternal(JsonGenerator generator, JsonpMapper mapper) {
         generator.writeKey("vector");
         generator.writeStartArray();
         for (float value : this.vector) {
-            generator.write(value);
+            BigDecimal b = new BigDecimal(value);
+            double T = b.setScale(6, HALF_UP).doubleValue();
+            generator.write(T);
         }
         generator.writeEnd();
 
diff --git a/java-client/src/test/java/org/opensearch/client/opensearch/_types/query_dsl/KnnQueryTest.java b/java-client/src/test/java/org/opensearch/client/opensearch/_types/query_dsl/KnnQueryTest.java
index df036f42c1..dbbf1cd176 100644
--- a/java-client/src/test/java/org/opensearch/client/opensearch/_types/query_dsl/KnnQueryTest.java
+++ b/java-client/src/test/java/org/opensearch/client/opensearch/_types/query_dsl/KnnQueryTest.java
@@ -11,4 +11,11 @@ public void toBuilder() {
 
         assertEquals(toJson(copied), toJson(origin));
     }
+
+    @Test
+    public void toBuilderPrecision() {
+        KnnQuery origin = new KnnQuery.Builder().field("field").vector(new float[] { 0.1f, 0.4f }).k(1).build();
+
+        assertEquals(toJson(origin), "{\"field\":{\"vector\":[0.1,0.4],\"k\":1}}");
+    }
 }
diff --git a/java-client/src/test/java/org/opensearch/client/opensearch/model/RequestEncodingTest.java b/java-client/src/test/java/org/opensearch/client/opensearch/model/RequestEncodingTest.java
index 61a57e1091..5941de2b01 100644
--- a/java-client/src/test/java/org/opensearch/client/opensearch/model/RequestEncodingTest.java
+++ b/java-client/src/test/java/org/opensearch/client/opensearch/model/RequestEncodingTest.java
@@ -33,6 +33,7 @@
 package org.opensearch.client.opensearch.model;
 
 import org.junit.Test;
+import org.opensearch.client.json.jackson.JacksonJsonpMapper;
 import org.opensearch.client.json.jsonb.JsonbJsonpMapper;
 import org.opensearch.client.opensearch.core.SearchRequest;
 
@@ -61,4 +62,20 @@ public void testParametersNotInJson() {
         assertNull(request.q());
 
     }
+
+    @Test
+    public void testKnnVectorPrecision() {
+
+        float[] vector = { 0.4f, 0.3f };
+        SearchRequest request = new SearchRequest.Builder().q("knn").query(q -> q.knn(k -> k.field("values").vector(vector).k(1))).build();
+
+        JacksonJsonpMapper mapper = new JacksonJsonpMapper();
+        String str = toJson(request, mapper);
+        assertEquals("{\"query\":{\"knn\":{\"values\":{\"vector\":[0.4,0.3],\"k\":1}}}}", str);
+
+        request = fromJson(str, SearchRequest.class, mapper);
+
+        assertTrue(request.query().isKnn());
+        assertNull(request.q());
+    }
 }