diff --git a/lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90HnswVectorsFormat.java b/lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90HnswVectorsFormat.java
index 213e443ba03..90875d9e3f5 100644
--- a/lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90HnswVectorsFormat.java
+++ b/lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90HnswVectorsFormat.java
@@ -112,4 +112,13 @@ public final class Lucene90HnswVectorsFormat extends KnnVectorsFormat {
   public KnnVectorsReader fieldsReader(SegmentReadState state) throws IOException {
     return new Lucene90HnswVectorsReader(state);
   }
+
+  @Override
+  public String toString() {
+    return "Lucene90HnswVectorsFormat(name = Lucene90HnswVectorsFormat, maxConn = "
+        + maxConn
+        + ", beamWidth="
+        + beamWidth
+        + ")";
+  }
 }
diff --git a/lucene/core/src/test/org/apache/lucene/codecs/lucene90/TestLucene90HnswVectorsFormat.java b/lucene/core/src/test/org/apache/lucene/codecs/lucene90/TestLucene90HnswVectorsFormat.java
index ae133bc58bb..e13840b97db 100644
--- a/lucene/core/src/test/org/apache/lucene/codecs/lucene90/TestLucene90HnswVectorsFormat.java
+++ b/lucene/core/src/test/org/apache/lucene/codecs/lucene90/TestLucene90HnswVectorsFormat.java
@@ -16,7 +16,12 @@
  */
 package org.apache.lucene.codecs.lucene90;
 
+import static com.carrotsearch.randomizedtesting.RandomizedTest.randomIntBetween;
+import static org.apache.lucene.codecs.lucene90.Lucene90HnswVectorsFormat.DEFAULT_BEAM_WIDTH;
+import static org.apache.lucene.codecs.lucene90.Lucene90HnswVectorsFormat.DEFAULT_MAX_CONN;
+
 import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.codecs.KnnVectorsFormat;
 import org.apache.lucene.index.BaseKnnVectorsFormatTestCase;
 import org.apache.lucene.util.TestUtil;
 
@@ -25,4 +30,26 @@ public class TestLucene90HnswVectorsFormat extends BaseKnnVectorsFormatTestCase
   protected Codec getCodec() {
     return TestUtil.getDefaultCodec();
   }
+
+  public void testToString() {
+    int maxConn = randomIntBetween(DEFAULT_MAX_CONN - 10, DEFAULT_MAX_CONN + 10);
+    int beamWidth = randomIntBetween(DEFAULT_BEAM_WIDTH - 50, DEFAULT_BEAM_WIDTH + 50);
+    Codec customCodec =
+        new Lucene90Codec() {
+          @Override
+          public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
+            return new Lucene90HnswVectorsFormat(maxConn, beamWidth);
+          }
+        };
+    String expectedString =
+        "Lucene90HnswVectorsFormat(name = Lucene90HnswVectorsFormat, maxConn = "
+            + maxConn
+            + ", beamWidth="
+            + beamWidth
+            + ")";
+    assert (((Lucene90Codec) customCodec)
+        .getKnnVectorsFormatForField("bogus_field")
+        .toString()
+        .equals(expectedString));
+  }
 }