diff --git a/java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/telemetry/HttpTracingRequestInitializer.java b/java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/telemetry/HttpTracingRequestInitializer.java
index d34409d44028..3ff398e2eef0 100644
--- a/java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/telemetry/HttpTracingRequestInitializer.java
+++ b/java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/telemetry/HttpTracingRequestInitializer.java
@@ -20,10 +20,15 @@
 import com.google.api.core.BetaApi;
 import com.google.api.core.InternalApi;
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.io.CountingInputStream;
 import io.opentelemetry.api.common.AttributeKey;
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.api.trace.Tracer;
+import java.io.FilterInputStream;
 import java.io.IOException;
+import java.io.InputStream;
+import java.lang.reflect.Field;
+import org.jspecify.annotations.NonNull;
 
 /**
  * HttpRequestInitializer that wraps a delegate initializer, intercepts all HTTP requests, adds
@@ -50,6 +55,7 @@ public class HttpTracingRequestInitializer implements HttpRequestInitializer {
       AttributeKey.longKey("http.response.body.size");
 
   @VisibleForTesting static final String HTTP_RPC_SYSTEM_NAME = "http";
+  @VisibleForTesting static final String GZIP_ENCODING = "gzip";
 
   private static final java.util.Set<String> REDACTED_QUERY_PARAMETERS =
       com.google.common.collect.ImmutableSet.of(
@@ -137,7 +143,42 @@ static void addResponseBodySizeToSpan(HttpResponse response, Span span) {
     if (contentLength != null && contentLength > 0) {
       span.setAttribute(HTTP_RESPONSE_BODY_SIZE, contentLength);
     }
-    // TODO handle chunked responses
+    // For compressed responses without Content-Length, we need to wrap the response to get the
+    // actual size
+    if (GZIP_ENCODING.equals(response.getContentEncoding())) {
+      getResponseBodySizeForCompressedResponse(response, span);
+    }
+  }
+
+  /**
+   * Wraps the response's input stream with a CountingInputStream to track bytes read. This handles
+   * compressed transfer encoding where Content-Length is not available.
+   */
+  private static void getResponseBodySizeForCompressedResponse(HttpResponse response, Span span) {
+    try {
+      InputStream content = response.getContent();
+      if (content == null) {
+        return;
+      }
+
+      InputStream wrappedStream = getWrappedInputStream(span, content);
+      Field contentField = HttpResponse.class.getDeclaredField("content");
+      contentField.setAccessible(true);
+      contentField.set(response, wrappedStream);
+    } catch (Exception e) {
+      // Ignore - stream wrapping failed, we will not track response size
+    }
+  }
+
+  private static @NonNull InputStream getWrappedInputStream(Span span, InputStream content) {
+    CountingInputStream counter = new CountingInputStream(content);
+    return new FilterInputStream(counter) {
+      @Override
+      public void close() throws IOException {
+        super.close();
+        span.setAttribute(HTTP_RESPONSE_BODY_SIZE, counter.getCount());
+      }
+    };
   }
 
   /** Removes credentials from URL. */
diff --git a/java-bigquery/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/telemetry/HttpTracingRequestInitializerTest.java b/java-bigquery/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/telemetry/HttpTracingRequestInitializerTest.java
index 0bf0012be30e..c0d8033ab6eb 100644
--- a/java-bigquery/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/telemetry/HttpTracingRequestInitializerTest.java
+++ b/java-bigquery/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/telemetry/HttpTracingRequestInitializerTest.java
@@ -53,8 +53,13 @@
 import io.opentelemetry.sdk.trace.SdkTracerProvider;
 import io.opentelemetry.sdk.trace.data.SpanData;
 import io.opentelemetry.sdk.trace.export.SimpleSpanProcessor;
+
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
+import java.util.zip.GZIPOutputStream;
+
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
@@ -430,4 +435,47 @@ private void closeAndVerifySpanData(
       assertNull(span.getAttributes().get(HttpTracingRequestInitializer.HTTP_RESPONSE_BODY_SIZE));
     }
   }
+
+  @Test
+  public void testCompressedResponseBodySizeTracking() throws IOException {
+    String responseBody = "chunked response data";
+    ByteArrayOutputStream responseStream = new ByteArrayOutputStream();
+    try (GZIPOutputStream gzipOut = new GZIPOutputStream(responseStream)) {
+      gzipOut.write(responseBody.getBytes(StandardCharsets.UTF_8));
+    }
+    byte[] compressedData = responseStream.toByteArray();
+
+    HttpTransport transport =
+        new MockHttpTransport() {
+          @Override
+          public LowLevelHttpRequest buildRequest(String method, String url) {
+            return new MockLowLevelHttpRequest() {
+              @Override
+              public LowLevelHttpResponse execute() {
+                MockLowLevelHttpResponse response = new MockLowLevelHttpResponse();
+                response.setContentEncoding(HttpTracingRequestInitializer.GZIP_ENCODING);
+                response.setStatusCode(200);
+                response.setContent(new java.io.ByteArrayInputStream(compressedData));
+                return response;
+              }
+            };
+          }
+        };
+
+    HttpRequest request = buildGetRequest(transport, initializer, BASE_URL);
+    HttpResponse response = request.execute();
+    // Read the entire response body (this triggers the counting)
+    response.parseAsString();
+
+    response.disconnect();
+    spanScope.close();
+    parentSpan.end();
+    List<SpanData> spans = spanExporter.getFinishedSpanItems();
+    assertEquals(1, spans.size());
+    SpanData span = spans.get(0);
+
+    assertEquals(
+        (long) responseBody.length(),
+        span.getAttributes().get(HttpTracingRequestInitializer.HTTP_RESPONSE_BODY_SIZE));
+  }
 }