diff --git a/java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/ContentMaker.java b/java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/ContentMaker.java
index e9338b91eb50..1816e377896e 100644
--- a/java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/ContentMaker.java
+++ b/java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/ContentMaker.java
@@ -16,8 +16,11 @@
 
 package com.google.cloud.vertexai.generativeai;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 import com.google.cloud.vertexai.api.Content;
 import com.google.cloud.vertexai.api.Part;
+import com.google.common.base.Strings;
 
 /** Helper class to create content. */
 public class ContentMaker {
@@ -34,6 +37,7 @@ public static ContentMakerForRole forRole(String role) {
   }
 
   private static Content fromStringWithRole(String role, String text) {
+    checkArgument(!Strings.isNullOrEmpty(text), "text message can't be null or empty.");
     return Content.newBuilder().addParts(Part.newBuilder().setText(text)).setRole(role).build();
   }
 
diff --git a/java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/GenerativeModel.java b/java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/GenerativeModel.java
index 815122a01a3c..4312e422525e 100644
--- a/java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/GenerativeModel.java
+++ b/java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/GenerativeModel.java
@@ -228,7 +228,6 @@ public GenerativeModel withTools(List<Tool> tools) {
    */
   @BetaApi
   public CountTokensResponse countTokens(String text) throws IOException {
-    // TODO(b/330402637): Check null and empty values for the input string.
     return countTokens(ContentMaker.fromString(text));
   }
 
@@ -255,6 +254,9 @@ public CountTokensResponse countTokens(Content content) throws IOException {
    */
   @BetaApi
   public CountTokensResponse countTokens(List<Content> contents) throws IOException {
+    if (contents == null || contents.isEmpty()) {
+      throw new IllegalArgumentException("contents can't be null or empty.");
+    }
     CountTokensRequest request =
         CountTokensRequest.newBuilder()
             .setEndpoint(resourceName)
@@ -287,7 +289,6 @@ private CountTokensResponse countTokensFromRequest(CountTokensRequest request)
    * @throws IOException if an I/O error occurs while making the API call
    */
   public GenerateContentResponse generateContent(String text) throws IOException {
-    // TODO(b/330402637): Check null and empty values for the input string.
     return generateContent(ContentMaker.fromString(text));
   }
 
@@ -447,6 +448,9 @@ private ApiFuture<GenerateContentResponse> generateContentAsync(GenerateContentR
    * contents and model configurations.
    */
   private GenerateContentRequest buildGenerateContentRequest(List<Content> contents) {
+    if (contents == null || contents.isEmpty()) {
+      throw new IllegalArgumentException("contents can't be null or empty.");
+    }
     return GenerateContentRequest.newBuilder()
         .setModel(resourceName)
         .addAllContents(contents)
diff --git a/java-vertexai/google-cloud-vertexai/src/test/java/com/google/cloud/vertexai/generativeai/ContentMakerTest.java b/java-vertexai/google-cloud-vertexai/src/test/java/com/google/cloud/vertexai/generativeai/ContentMakerTest.java
index d0813890ecea..3a318aaeb453 100644
--- a/java-vertexai/google-cloud-vertexai/src/test/java/com/google/cloud/vertexai/generativeai/ContentMakerTest.java
+++ b/java-vertexai/google-cloud-vertexai/src/test/java/com/google/cloud/vertexai/generativeai/ContentMakerTest.java
@@ -17,6 +17,7 @@
 package com.google.cloud.vertexai.generativeai;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
 
 import com.google.cloud.vertexai.api.Content;
 import com.google.protobuf.ByteString;
@@ -38,6 +39,24 @@ public void fromString_returnsContentWithText() {
     assertThat(content.getParts(0).getText()).isEqualTo(stringInput);
   }
 
+  @Test
+  public void fromString_throwsIllegalArgumentException_withEmptyString() {
+    String stringInput = "";
+
+    IllegalArgumentException thrown =
+        assertThrows(IllegalArgumentException.class, () -> ContentMaker.fromString(stringInput));
+    assertThat(thrown).hasMessageThat().isEqualTo("text message can't be null or empty.");
+  }
+
+  @Test
+  public void fromString_throwsIllegalArgumentException_withNullString() {
+    String stringInput = null;
+
+    IllegalArgumentException thrown =
+        assertThrows(IllegalArgumentException.class, () -> ContentMaker.fromString(stringInput));
+    assertThat(thrown).hasMessageThat().isEqualTo("text message can't be null or empty.");
+  }
+
   @Test
   public void forRole_returnsContentWithArbitraryRoleSet() {
     // Although in our docstring, we said only three roles are acceptable, we make sure the code
diff --git a/java-vertexai/google-cloud-vertexai/src/test/java/com/google/cloud/vertexai/generativeai/GenerativeModelTest.java b/java-vertexai/google-cloud-vertexai/src/test/java/com/google/cloud/vertexai/generativeai/GenerativeModelTest.java
index 84f8d0b61fa5..2495fe0694e9 100644
--- a/java-vertexai/google-cloud-vertexai/src/test/java/com/google/cloud/vertexai/generativeai/GenerativeModelTest.java
+++ b/java-vertexai/google-cloud-vertexai/src/test/java/com/google/cloud/vertexai/generativeai/GenerativeModelTest.java
@@ -48,6 +48,7 @@
 import com.google.cloud.vertexai.api.Type;
 import com.google.cloud.vertexai.api.VertexAISearch;
 import java.lang.reflect.Field;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
@@ -451,6 +452,16 @@ public void testGenerateContentwithFluentApi() throws Exception {
     assertThat(request.getValue().getTools(0)).isEqualTo(TOOL);
   }
 
+  @Test
+  public void generateContent_withNullContents_throws() throws Exception {
+    model = new GenerativeModel(MODEL_NAME, vertexAi);
+    List<Content> contents = null;
+
+    IllegalArgumentException thrown =
+        assertThrows(IllegalArgumentException.class, () -> model.generateContent(contents));
+    assertThat(thrown).hasMessageThat().isEqualTo("contents can't be null or empty.");
+  }
+
   @Test
   public void testGenerateContentStreamwithText() throws Exception {
     model = new GenerativeModel(MODEL_NAME, vertexAi);
@@ -635,6 +646,16 @@ public void testGenerateContentStreamwithFluentApi() throws Exception {
     assertThat(request.getValue().getTools(0)).isEqualTo(TOOL);
   }
 
+  @Test
+  public void generateContentStream_withEmptyContents_throws() throws Exception {
+    model = new GenerativeModel(MODEL_NAME, vertexAi);
+    List<Content> contents = new ArrayList<>();
+
+    IllegalArgumentException thrown =
+        assertThrows(IllegalArgumentException.class, () -> model.generateContentStream(contents));
+    assertThat(thrown).hasMessageThat().isEqualTo("contents can't be null or empty.");
+  }
+
   @Test
   public void generateContentAsync_withText_sendsCorrectRequest() throws Exception {
     model = new GenerativeModel(MODEL_NAME, vertexAi);