diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java
index af7472e96..1ed5e2254 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java
@@ -27,6 +27,7 @@
 import com.google.api.gax.batching.BatchingSettings;
 import com.google.api.gax.batching.FlowControlSettings;
 import com.google.api.gax.batching.FlowController;
+import com.google.api.gax.batching.FlowController.LimitExceededBehavior;
 import com.google.api.gax.core.BackgroundResource;
 import com.google.api.gax.core.BackgroundResourceAggregation;
 import com.google.api.gax.core.CredentialsProvider;
@@ -779,6 +780,11 @@ public Builder setBatchingSettings(BatchingSettings batchingSettings) {
       Preconditions.checkArgument(batchingSettings.getRequestByteThreshold() > 0);
       Preconditions.checkNotNull(batchingSettings.getDelayThreshold());
       Preconditions.checkArgument(batchingSettings.getDelayThreshold().toMillis() > 0);
+      FlowControlSettings flowControlSettings = batchingSettings.getFlowControlSettings();
+      if (flowControlSettings.getLimitExceededBehavior() != LimitExceededBehavior.Ignore) {
+        Preconditions.checkArgument(flowControlSettings.getMaxOutstandingElementCount() > 0);
+        Preconditions.checkArgument(flowControlSettings.getMaxOutstandingRequestBytes() > 0);
+      }
       this.batchingSettings = batchingSettings;
       return this;
     }
@@ -859,6 +865,12 @@ private static class MessageFlowController {
     }
 
     void acquire(long messageSize) throws FlowController.FlowControlException {
+      if (messageSize > byteLimit) {
+        logger.log(
+            Level.WARNING,
+            "Attempted to publish message with byte size > request byte flow control limit.");
+        throw new FlowController.MaxOutstandingRequestBytesReachedException(byteLimit);
+      }
       lock.lock();
       try {
         if (outstandingMessages >= messageLimit
diff --git a/google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/v1/PublisherImplTest.java b/google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/v1/PublisherImplTest.java
index 3da657061..c41931de6 100644
--- a/google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/v1/PublisherImplTest.java
+++ b/google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/v1/PublisherImplTest.java
@@ -1019,7 +1019,57 @@ public void testShutDown() throws Exception {
   }
 
   @Test
-  public void testPublishFlowControl_throwException() throws Exception {
+  public void invalidFlowControlBytes_throwException() throws Exception {
+    try {
+      Publisher publisher =
+          getTestPublisherBuilder()
+              .setBatchingSettings(
+                  Publisher.Builder.DEFAULT_BATCHING_SETTINGS
+                      .toBuilder()
+                      .setElementCountThreshold(1L)
+                      .setDelayThreshold(Duration.ofSeconds(5))
+                      .setFlowControlSettings(
+                          FlowControlSettings.newBuilder()
+                              .setLimitExceededBehavior(
+                                  FlowController.LimitExceededBehavior.ThrowException)
+                              .setMaxOutstandingElementCount(1L)
+                              .setMaxOutstandingRequestBytes(0L)
+                              .build())
+                      .build())
+              .build();
+      fail("Expected an IllegalArgumentException");
+    } catch (Exception e) {
+      assertThat(e).isInstanceOf(IllegalArgumentException.class);
+    }
+  }
+
+  @Test
+  public void invalidFlowControlElementCount_throwException() throws Exception {
+    try {
+      Publisher publisher =
+          getTestPublisherBuilder()
+              .setBatchingSettings(
+                  Publisher.Builder.DEFAULT_BATCHING_SETTINGS
+                      .toBuilder()
+                      .setElementCountThreshold(1L)
+                      .setDelayThreshold(Duration.ofSeconds(5))
+                      .setFlowControlSettings(
+                          FlowControlSettings.newBuilder()
+                              .setLimitExceededBehavior(
+                                  FlowController.LimitExceededBehavior.ThrowException)
+                              .setMaxOutstandingElementCount(0L)
+                              .setMaxOutstandingRequestBytes(1000L)
+                              .build())
+                      .build())
+              .build();
+      fail("Expected an IllegalArgumentException");
+    } catch (Exception e) {
+      assertThat(e).isInstanceOf(IllegalArgumentException.class);
+    }
+  }
+
+  @Test
+  public void testMessageExceedsFlowControlLimits_throwException() throws Exception {
     Publisher publisher =
         getTestPublisherBuilder()
             .setExecutorProvider(SINGLE_THREAD_EXECUTOR)
@@ -1030,31 +1080,49 @@ public void testPublishFlowControl_throwException() throws Exception {
                     .setDelayThreshold(Duration.ofSeconds(5))
                     .setFlowControlSettings(
                         FlowControlSettings.newBuilder()
-                            .setLimitExceededBehavior(
-                                FlowController.LimitExceededBehavior.ThrowException)
+                            .setLimitExceededBehavior(FlowController.LimitExceededBehavior.Block)
                             .setMaxOutstandingElementCount(1L)
-                            .setMaxOutstandingRequestBytes(10L)
+                            .setMaxOutstandingRequestBytes(1L)
                             .build())
                     .build())
             .build();
 
-    // Sending a message that is too large results in an exception.
-    ApiFuture<String> publishFuture1 = sendTestMessage(publisher, "AAAAAAAAAAA");
     try {
-      publishFuture1.get();
-      fail("Should have thrown an FlowController.MaxOutstandingRequestBytesReachedException");
+      sendTestMessage(publisher, "AAAAAAAAAAAAAAAAAAAAA").get();
+      fail("Should have thrown a FlowController.MaxOutstandingRequestBytesReachedException");
     } catch (ExecutionException e) {
       assertThat(e.getCause())
           .isInstanceOf(FlowController.MaxOutstandingRequestBytesReachedException.class);
     }
+  }
 
-    // Sending a second message succeeds.
-    ApiFuture<String> publishFuture2 = sendTestMessage(publisher, "AAAA");
+  @Test
+  public void testPublishFlowControl_throwException() throws Exception {
+    Publisher publisher =
+        getTestPublisherBuilder()
+            .setExecutorProvider(SINGLE_THREAD_EXECUTOR)
+            .setBatchingSettings(
+                Publisher.Builder.DEFAULT_BATCHING_SETTINGS
+                    .toBuilder()
+                    .setElementCountThreshold(1L)
+                    .setDelayThreshold(Duration.ofSeconds(5))
+                    .setFlowControlSettings(
+                        FlowControlSettings.newBuilder()
+                            .setLimitExceededBehavior(
+                                FlowController.LimitExceededBehavior.ThrowException)
+                            .setMaxOutstandingElementCount(1L)
+                            .setMaxOutstandingRequestBytes(10L)
+                            .build())
+                    .build())
+            .build();
+
+    // Sending a message less than the byte limit succeeds.
+    ApiFuture<String> publishFuture1 = sendTestMessage(publisher, "AAAA");
 
-    // Sending a third message fails because of the outstanding message.
-    ApiFuture<String> publishFuture3 = sendTestMessage(publisher, "AA");
+    // Sending another message fails because of the outstanding message.
+    ApiFuture<String> publishFuture2 = sendTestMessage(publisher, "AA");
     try {
-      publishFuture3.get();
+      publishFuture2.get();
       fail("Should have thrown an FlowController.MaxOutstandingElementCountReachedException");
     } catch (ExecutionException e) {
       assertThat(e.getCause())
@@ -1062,7 +1130,7 @@ public void testPublishFlowControl_throwException() throws Exception {
     }
 
     testPublisherServiceImpl.addPublishResponse(PublishResponse.newBuilder().addMessageIds("1"));
-    assertEquals("1", publishFuture2.get());
+    assertEquals("1", publishFuture1.get());
 
     // Sending another message succeeds.
     ApiFuture<String> publishFuture4 = sendTestMessage(publisher, "AAAA");
@@ -1091,22 +1159,27 @@ public void testPublishFlowControl_throwExceptionWithOrderingKey() throws Except
             .setEnableMessageOrdering(true)
             .build();
 
-    // Sending a message that is too large results in an exception.
-    ApiFuture<String> publishFuture1 =
-        sendTestMessageWithOrderingKey(publisher, "AAAAAAAAAAA", "a");
+    // Sending a message less than the byte limit succeeds.
+    ApiFuture<String> publishFuture1 = sendTestMessageWithOrderingKey(publisher, "AAAA", "a");
+
+    // Sending another message fails because of the outstanding message.
+    ApiFuture<String> publishFuture2 = sendTestMessageWithOrderingKey(publisher, "AA", "a");
     try {
-      publishFuture1.get();
-      fail("Should have thrown an FlowController.MaxOutstandingRequestBytesReachedException");
+      publishFuture2.get();
+      fail("Should have thrown an FlowController.MaxOutstandingElementCountReachedException");
     } catch (ExecutionException e) {
       assertThat(e.getCause())
-          .isInstanceOf(FlowController.MaxOutstandingRequestBytesReachedException.class);
+          .isInstanceOf(FlowController.MaxOutstandingElementCountReachedException.class);
     }
 
-    // Sending a second message for the same ordering key fails because the first one failed.
-    ApiFuture<String> publishFuture2 = sendTestMessageWithOrderingKey(publisher, "AAAA", "a");
+    testPublisherServiceImpl.addPublishResponse(PublishResponse.newBuilder().addMessageIds("1"));
+    assertEquals("1", publishFuture1.get());
+
+    // Sending another message for the same ordering key fails because the one before failed.
+    ApiFuture<String> publishFuture3 = sendTestMessageWithOrderingKey(publisher, "AAAA", "a");
     try {
-      publishFuture2.get();
-      Assert.fail("This should fail.");
+      publishFuture3.get();
+      fail("This should fail.");
     } catch (ExecutionException e) {
       assertEquals(SequentialExecutorService.CallbackExecutor.CANCELLATION_EXCEPTION, e.getCause());
     }