diff --git a/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1beta2/StreamWriterV2.java b/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1beta2/StreamWriterV2.java
index 10ed99d137..8debea15f9 100644
--- a/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1beta2/StreamWriterV2.java
+++ b/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1beta2/StreamWriterV2.java
@@ -22,6 +22,7 @@
 import com.google.common.base.Preconditions;
 import com.google.common.util.concurrent.Uninterruptibles;
 import io.grpc.Status;
+import io.grpc.Status.Code;
 import io.grpc.StatusRuntimeException;
 import java.util.Deque;
 import java.util.LinkedList;
@@ -39,8 +40,6 @@
  *
  * <p>TODO: Attach schema.
  *
- * <p>TODO: Add max size check.
- *
  * <p>TODO: Add inflight control.
  *
  * <p>TODO: Attach traceId.
@@ -94,6 +93,11 @@ public class StreamWriterV2 implements AutoCloseable {
    */
   private Thread appendThread;
 
+  /** The maximum size of one request. Defined by the API. */
+  public static long getApiMaxRequestBytes() {
+    return 8L * 1000L * 1000L; // 8 megabytes (https://en.wikipedia.org/wiki/Megabyte)
+  }
+
   private StreamWriterV2(Builder builder) {
     this.lock = new ReentrantLock();
     this.hasMessageInWaitingQueue = lock.newCondition();
@@ -154,6 +158,17 @@ public void run() {
    */
   public ApiFuture<AppendRowsResponse> append(AppendRowsRequest message) {
     AppendRequestAndResponse requestWrapper = new AppendRequestAndResponse(message);
+    if (requestWrapper.messageSize > getApiMaxRequestBytes()) {
+      requestWrapper.appendResult.setException(
+          new StatusRuntimeException(
+              Status.fromCode(Code.INVALID_ARGUMENT)
+                  .withDescription(
+                      "MessageSize is too large. Max allow: "
+                          + getApiMaxRequestBytes()
+                          + " Actual: "
+                          + requestWrapper.messageSize)));
+      return requestWrapper.appendResult;
+    }
     this.lock.lock();
     try {
       if (userClosed) {
@@ -355,10 +370,12 @@ public StreamWriterV2 build() {
   private static final class AppendRequestAndResponse {
     final SettableApiFuture<AppendRowsResponse> appendResult;
     final AppendRowsRequest message;
+    final long messageSize;
 
     AppendRequestAndResponse(AppendRowsRequest message) {
       this.appendResult = SettableApiFuture.create();
       this.message = message;
+      this.messageSize = message.getProtoRows().getSerializedSize();
     }
   }
 }
diff --git a/google-cloud-bigquerystorage/src/test/java/com/google/cloud/bigquery/storage/v1beta2/StreamWriterV2Test.java b/google-cloud-bigquerystorage/src/test/java/com/google/cloud/bigquery/storage/v1beta2/StreamWriterV2Test.java
index c50e5abb70..4d6fba9dcd 100644
--- a/google-cloud-bigquerystorage/src/test/java/com/google/cloud/bigquery/storage/v1beta2/StreamWriterV2Test.java
+++ b/google-cloud-bigquerystorage/src/test/java/com/google/cloud/bigquery/storage/v1beta2/StreamWriterV2Test.java
@@ -26,6 +26,7 @@
 import com.google.api.gax.rpc.ApiException;
 import com.google.api.gax.rpc.StatusCode.Code;
 import com.google.cloud.bigquery.storage.test.Test.FooType;
+import com.google.common.base.Strings;
 import com.google.protobuf.DescriptorProtos;
 import com.google.protobuf.Int64Value;
 import io.grpc.Status;
@@ -288,6 +289,20 @@ public void serverCloseWhileRequestsInflight() throws Exception {
     }
 
     writer.close();
-    ;
+  }
+
+  @Test
+  public void testMessageTooLarge() {
+    StreamWriterV2 writer = getTestStreamWriterV2();
+
+    String oversized = Strings.repeat("a", (int) (StreamWriterV2.getApiMaxRequestBytes() + 1));
+    ApiFuture<AppendRowsResponse> appendFuture1 = sendTestMessage(writer, new String[] {oversized});
+    assertTrue(appendFuture1.isDone());
+    StatusRuntimeException actualError =
+        assertFutureException(StatusRuntimeException.class, appendFuture1);
+    assertEquals(Status.Code.INVALID_ARGUMENT, actualError.getStatus().getCode());
+    assertTrue(actualError.getStatus().getDescription().contains("MessageSize is too large"));
+
+    writer.close();
   }
 }