diff --git a/data-prepper-plugins/opensearch/README.md b/data-prepper-plugins/opensearch/README.md
index 14fad00846..244307e466 100644
--- a/data-prepper-plugins/opensearch/README.md
+++ b/data-prepper-plugins/opensearch/README.md
@@ -157,6 +157,9 @@ Besides common metrics in [AbstractSink](https://github.com/opensearch-project/d
 - `documentsSuccessFirstAttempt`: measures number of documents successfully sent to ES by bulk requests on first attempt.
 - `documentErrors`: measures number of documents failed to be sent by bulk requests.
 
+### Distribution Summary
+- `bulkRequestSizeBytes`: measures the distribution of bulk request's payload sizes in bytes.
+
 ## Developer Guide
 
 This plugin is compatible with Java 8. See
diff --git a/data-prepper-plugins/opensearch/src/main/java/com/amazon/dataprepper/plugins/sink/opensearch/OpenSearchSink.java b/data-prepper-plugins/opensearch/src/main/java/com/amazon/dataprepper/plugins/sink/opensearch/OpenSearchSink.java
index 869bc5bf27..518da0f7cc 100644
--- a/data-prepper-plugins/opensearch/src/main/java/com/amazon/dataprepper/plugins/sink/opensearch/OpenSearchSink.java
+++ b/data-prepper-plugins/opensearch/src/main/java/com/amazon/dataprepper/plugins/sink/opensearch/OpenSearchSink.java
@@ -21,6 +21,7 @@
 import com.amazon.dataprepper.plugins.sink.opensearch.index.IndexManagerFactory;
 import com.amazon.dataprepper.plugins.sink.opensearch.index.IndexType;
 import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.DistributionSummary;
 import io.micrometer.core.instrument.Timer;
 import org.opensearch.action.DocWriteRequest;
 import org.opensearch.action.bulk.BulkRequest;
@@ -50,6 +51,7 @@
 public class OpenSearchSink extends AbstractSink<Record<Object>> {
   public static final String BULKREQUEST_LATENCY = "bulkRequestLatency";
   public static final String BULKREQUEST_ERRORS = "bulkRequestErrors";
+  public static final String BULKREQUEST_SIZE_BYTES = "bulkRequestSizeBytes";
 
   private static final Logger LOG = LoggerFactory.getLogger(OpenSearchSink.class);
   // Pulled from BulkRequest to make estimation of bytes consistent
@@ -68,10 +70,13 @@ public class OpenSearchSink extends AbstractSink<Record<Object>> {
 
   private final Timer bulkRequestTimer;
   private final Counter bulkRequestErrorsCounter;
+  private final DistributionSummary bulkRequestSizeBytesSummary;
+
   public OpenSearchSink(final PluginSetting pluginSetting) {
     super(pluginSetting);
     bulkRequestTimer = pluginMetrics.timer(BULKREQUEST_LATENCY);
     bulkRequestErrorsCounter = pluginMetrics.counter(BULKREQUEST_ERRORS);
+    bulkRequestSizeBytesSummary = pluginMetrics.summary(BULKREQUEST_SIZE_BYTES);
 
     this.openSearchSinkConfig = OpenSearchSinkConfiguration.readESConfig(pluginSetting);
     this.bulkSize = ByteSizeUnit.MB.toBytes(openSearchSinkConfig.getIndexConfiguration().getBulkSize());
@@ -165,6 +170,7 @@ private void flushBatch(final BulkRequest bulkRequest) {
     bulkRequestTimer.record(() -> {
       try {
         bulkRetryStrategy.execute(bulkRequest);
+        bulkRequestSizeBytesSummary.record(bulkRequest.estimatedSizeInBytes());
       } catch (final InterruptedException e) {
         LOG.error("Unexpected Interrupt:", e);
         bulkRequestErrorsCounter.increment();
diff --git a/data-prepper-plugins/opensearch/src/test/java/com/amazon/dataprepper/plugins/sink/opensearch/OpenSearchSinkIT.java b/data-prepper-plugins/opensearch/src/test/java/com/amazon/dataprepper/plugins/sink/opensearch/OpenSearchSinkIT.java
index 91ee237761..d5bacfa3a9 100644
--- a/data-prepper-plugins/opensearch/src/test/java/com/amazon/dataprepper/plugins/sink/opensearch/OpenSearchSinkIT.java
+++ b/data-prepper-plugins/opensearch/src/test/java/com/amazon/dataprepper/plugins/sink/opensearch/OpenSearchSinkIT.java
@@ -191,6 +191,17 @@ public void testOutputRawSpanDefault() throws IOException, InterruptedException
                     .add(BulkRetryStrategy.DOCUMENT_ERRORS).toString());
     assertEquals(1, documentErrorsMeasurements.size());
     assertEquals(0.0, documentErrorsMeasurements.get(0).getValue(), 0);
+
+    /**
+     * Metrics: Bulk Request Size in Bytes
+     */
+    final List<Measurement> bulkRequestSizeBytesMetrics = MetricsTestUtil.getMeasurementList(
+            new StringJoiner(MetricNames.DELIMITER).add(PIPELINE_NAME).add(PLUGIN_NAME)
+                    .add(OpenSearchSink.BULKREQUEST_SIZE_BYTES).toString());
+    assertEquals(3, bulkRequestSizeBytesMetrics.size());
+    assertEquals(1.0, bulkRequestSizeBytesMetrics.get(0).getValue(), 0);
+    assertEquals(2188.0, bulkRequestSizeBytesMetrics.get(1).getValue(), 0);
+    assertEquals(2188.0, bulkRequestSizeBytesMetrics.get(2).getValue(), 0);
   }
 
   public void testOutputRawSpanWithDLQ() throws IOException, InterruptedException {
@@ -233,6 +244,18 @@ public void testOutputRawSpanWithDLQ() throws IOException, InterruptedException
                     .add(BulkRetryStrategy.DOCUMENT_ERRORS).toString());
     assertEquals(1, documentErrorsMeasurements.size());
     assertEquals(1.0, documentErrorsMeasurements.get(0).getValue(), 0);
+
+    /**
+     * Metrics: Bulk Request Size in Bytes
+     */
+    final List<Measurement> bulkRequestSizeBytesMetrics = MetricsTestUtil.getMeasurementList(
+            new StringJoiner(MetricNames.DELIMITER).add(PIPELINE_NAME).add(PLUGIN_NAME)
+                    .add(OpenSearchSink.BULKREQUEST_SIZE_BYTES).toString());
+    assertEquals(3, bulkRequestSizeBytesMetrics.size());
+    assertEquals(1.0, bulkRequestSizeBytesMetrics.get(0).getValue(), 0);
+    assertEquals(2181.0, bulkRequestSizeBytesMetrics.get(1).getValue(), 0);
+    assertEquals(2181.0, bulkRequestSizeBytesMetrics.get(2).getValue(), 0);
+
   }
 
   public void testInstantiateSinkServiceMapDefault() throws IOException {
@@ -277,6 +300,17 @@ public void testOutputServiceMapDefault() throws IOException, InterruptedExcepti
     // COUNT
     Assert.assertEquals(1.0, bulkRequestLatencies.get(0).getValue(), 0);
 
+    /**
+     * Metrics: Bulk Request Size in Bytes
+     */
+    final List<Measurement> bulkRequestSizeBytesMetrics = MetricsTestUtil.getMeasurementList(
+            new StringJoiner(MetricNames.DELIMITER).add(PIPELINE_NAME).add(PLUGIN_NAME)
+                    .add(OpenSearchSink.BULKREQUEST_SIZE_BYTES).toString());
+    assertEquals(3, bulkRequestSizeBytesMetrics.size());
+    assertEquals(1.0, bulkRequestSizeBytesMetrics.get(0).getValue(), 0);
+    assertEquals(309.0, bulkRequestSizeBytesMetrics.get(1).getValue(), 0);
+    assertEquals(309.0, bulkRequestSizeBytesMetrics.get(2).getValue(), 0);
+
     // Check restart for index already exists
     sink = new OpenSearchSink(pluginSetting);
     sink.shutdown();