diff --git a/oauth2_http/javatests/com/google/auth/oauth2/CredentialsTimeoutTest.java b/oauth2_http/javatests/com/google/auth/oauth2/CredentialsTimeoutTest.java
new file mode 100644
index 000000000..0a6d0b2a2
--- /dev/null
+++ b/oauth2_http/javatests/com/google/auth/oauth2/CredentialsTimeoutTest.java
@@ -0,0 +1,287 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *
+ *    * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT of THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.auth.oauth2;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+import com.google.api.client.http.javanet.NetHttpTransport;
+import com.google.api.client.json.GenericJson;
+import com.google.auth.http.HttpTransportFactory;
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.InetAddress;
+import java.net.SocketTimeoutException;
+import java.security.GeneralSecurityException;
+import java.security.SecureRandom;
+import java.security.cert.X509Certificate;
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+import java.util.Collections;
+import java.util.Date;
+import java.util.concurrent.TimeUnit;
+import javax.net.ssl.HostnameVerifier;
+import javax.net.ssl.SSLContext;
+import javax.net.ssl.SSLSocketFactory;
+import javax.net.ssl.TrustManager;
+import javax.net.ssl.X509TrustManager;
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.MockWebServer;
+import okhttp3.tls.HandshakeCertificates;
+import okhttp3.tls.HeldCertificate;
+import org.junit.Test;
+
+public class CredentialsTimeoutTest {
+
+  private static final int TIMEOUT_MS = 1000; // 1 second
+
+  @Test
+  public void externalAccount_shouldTimeout() throws Exception {
+    // Create a server that is slow on the second (access token) request.
+    MockWebServer server = createExternalAccountMockServer(0, 2000);
+    server.start();
+
+    String tokenUrl = server.url("/token").toString();
+    String subjectTokenUrl = server.url("/subject_token").toString();
+
+    HttpTransportFactory transportFactory = createTimeoutTransportFactory(TIMEOUT_MS);
+    ExternalAccountCredentials credentials =
+        createExternalAccountCredentials(tokenUrl, subjectTokenUrl, transportFactory);
+
+    IOException exception = assertThrows(IOException.class, credentials::refresh);
+    assertTrue(exception.getCause() instanceof SocketTimeoutException);
+
+    server.shutdown();
+  }
+
+  @Test
+  public void externalAccount_shouldNotTimeout() throws Exception {
+    // Create a server that is faster than the client's timeout.
+    MockWebServer server = createExternalAccountMockServer(0, 500);
+    server.start();
+
+    String tokenUrl = server.url("/token").toString();
+    String subjectTokenUrl = server.url("/subject_token").toString();
+
+    HttpTransportFactory transportFactory = createTimeoutTransportFactory(TIMEOUT_MS);
+    ExternalAccountCredentials credentials =
+        createExternalAccountCredentials(tokenUrl, subjectTokenUrl, transportFactory);
+
+    credentials.refresh();
+    assertNotNull(credentials.getAccessToken());
+    assertEquals("test_token", credentials.getAccessToken().getTokenValue());
+
+    server.shutdown();
+  }
+
+  @Test
+  public void impersonatedCredentials_shouldTimeout() throws Exception {
+    // Create a server that is slower than the client's timeout.
+    MockWebServer server = createImpersonatedMockServer(2000);
+    server.start();
+
+    String iamEndpoint = server.url("/").toString();
+
+    HttpTransportFactory transportFactory = createTimeoutTransportFactory(TIMEOUT_MS);
+    ImpersonatedCredentials credentials =
+        createImpersonatedCredentials(iamEndpoint, transportFactory);
+
+    IOException exception = assertThrows(IOException.class, credentials::refresh);
+    assertTrue(exception.getCause() instanceof SocketTimeoutException);
+
+    server.shutdown();
+  }
+
+  @Test
+  public void impersonatedCredentials_shouldNotTimeout() throws Exception {
+    // Create a server that is faster than the client's timeout.
+    MockWebServer server = createImpersonatedMockServer(500);
+    server.start();
+
+    String iamEndpoint = server.url("/").toString();
+
+    HttpTransportFactory transportFactory = createTimeoutTransportFactory(TIMEOUT_MS);
+    ImpersonatedCredentials credentials =
+        createImpersonatedCredentials(iamEndpoint, transportFactory);
+
+    credentials.refresh();
+    assertNotNull(credentials.getAccessToken());
+    assertEquals("impersonated-token", credentials.getAccessToken().getTokenValue());
+
+    server.shutdown();
+  }
+
+  // Server and Credential Helper Methods
+
+  private static MockWebServer createExternalAccountMockServer(
+      int subjectTokenDelayMs, int accessTokenDelayMs) throws IOException {
+    MockWebServer server = new MockWebServer();
+    configureServerForHttps(server);
+
+    server.enqueue(
+        new MockResponse()
+            .setBody("dummy-subject-token")
+            .setBodyDelay(subjectTokenDelayMs, TimeUnit.MILLISECONDS));
+
+    String tokenResponse =
+        "{"
+            + "\"access_token\": \"test_token\","
+            + "\"issued_token_type\": \"urn:ietf:params:oauth:token-type:access_token\","
+            + "\"token_type\": \"Bearer\","
+            + "\"expires_in\": 3600"
+            + "}";
+    server.enqueue(
+        new MockResponse()
+            .setBody(tokenResponse)
+            .setBodyDelay(accessTokenDelayMs, TimeUnit.MILLISECONDS));
+
+    return server;
+  }
+
+  private static String getDefaultExpireTime() {
+    Calendar calendar = Calendar.getInstance();
+    calendar.setTime(new Date());
+    calendar.add(Calendar.SECOND, 300);
+    return new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'").format(calendar.getTime());
+  }
+
+  private static MockWebServer createImpersonatedMockServer(int delayMs) throws IOException {
+    MockWebServer server = new MockWebServer();
+    configureServerForHttps(server);
+
+    String expireTime = getDefaultExpireTime();
+    String tokenResponse =
+        "{"
+            + "\"accessToken\": \"impersonated-token\","
+            + "\"expireTime\": \""
+            + expireTime
+            + "\""
+            + "}";
+    server.enqueue(
+        new MockResponse().setBody(tokenResponse).setBodyDelay(delayMs, TimeUnit.MILLISECONDS));
+
+    return server;
+  }
+
+  private static void configureServerForHttps(MockWebServer server) throws IOException {
+    String localhost = InetAddress.getByName("localhost").getCanonicalHostName();
+    HeldCertificate localhostCertificate =
+        new HeldCertificate.Builder().addSubjectAlternativeName(localhost).build();
+    HandshakeCertificates serverCertificates =
+        new HandshakeCertificates.Builder().heldCertificate(localhostCertificate).build();
+    server.useHttps(serverCertificates.sslSocketFactory(), false);
+  }
+
+  private static ExternalAccountCredentials createExternalAccountCredentials(
+      String tokenUrl, String subjectTokenUrl, HttpTransportFactory transportFactory)
+      throws IOException {
+    GenericJson credentialSource = new GenericJson();
+    credentialSource.put("url", subjectTokenUrl);
+    credentialSource.put("headers", Collections.singletonMap("Metadata-Flavor", "Google"));
+
+    GenericJson json = new GenericJson();
+    json.put("type", "external_account");
+    json.put(
+        "audience",
+        "//iam.googleapis.com/projects/123/locations/global/workloadIdentityPools/pool/providers/provider");
+    json.put("subject_token_type", "urn:ietf:params:oauth:token-type:jwt");
+    json.put("token_url", tokenUrl);
+    json.put("credential_source", credentialSource);
+
+    return ExternalAccountCredentials.fromJson(json, transportFactory);
+  }
+
+  private static ImpersonatedCredentials createImpersonatedCredentials(
+      String iamEndpoint, HttpTransportFactory transportFactory) {
+    GoogleCredentials source =
+        new GoogleCredentials(new AccessToken("dummy-token", new Date())) {
+          @Override
+          public AccessToken refreshAccessToken() throws IOException {
+            // In a real scenario, this would fetch a new token. For this test,
+            // we just return a dummy token since the impersonation flow will
+            // use this credential's metadata, not its token.
+            return new AccessToken("refreshed-dummy-token", new Date());
+          }
+        };
+
+    return ImpersonatedCredentials.newBuilder()
+        .setSourceCredentials(source)
+        .setTargetPrincipal("test-sa@example.iam.gserviceaccount.com")
+        .setScopes(Collections.singletonList("https://www.googleapis.com/auth/cloud-platform"))
+        .setIamEndpointOverride(iamEndpoint)
+        .setHttpTransportFactory(transportFactory)
+        .build();
+  }
+
+  private static HttpTransportFactory createTimeoutTransportFactory(int timeoutMs) {
+    return () -> {
+      TrustManager[] trustAllCerts =
+          new TrustManager[] {
+            new X509TrustManager() {
+              public X509Certificate[] getAcceptedIssuers() {
+                return new X509Certificate[0];
+              }
+
+              public void checkClientTrusted(X509Certificate[] certs, String authType) {}
+
+              public void checkServerTrusted(X509Certificate[] certs, String authType) {}
+            }
+          };
+
+      SSLContext sslContext;
+      try {
+        sslContext = SSLContext.getInstance("TLS");
+        sslContext.init(null, trustAllCerts, new SecureRandom());
+      } catch (GeneralSecurityException e) {
+        throw new RuntimeException(e);
+      }
+      SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();
+      HostnameVerifier hostnameVerifier = (hostname, session) -> true;
+
+      NetHttpTransport.Builder builder =
+          new NetHttpTransport.Builder()
+              .setSslSocketFactory(sslSocketFactory)
+              .setHostnameVerifier(hostnameVerifier);
+
+      builder.setConnectionFactory(
+          url -> {
+            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
+            connection.setConnectTimeout(timeoutMs);
+            connection.setReadTimeout(timeoutMs);
+            return connection;
+          });
+      return builder.build();
+    };
+  }
+}
diff --git a/oauth2_http/pom.xml b/oauth2_http/pom.xml
index 42e81f2c5..ecf34feda 100644
--- a/oauth2_http/pom.xml
+++ b/oauth2_http/pom.xml
@@ -329,6 +329,18 @@
       <groupId>com.google.api</groupId>
       <artifactId>api-common</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.squareup.okhttp3</groupId>
+      <artifactId>mockwebserver</artifactId>
+      <version>5.3.2</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.squareup.okhttp3</groupId>
+      <artifactId>okhttp-tls</artifactId>
+      <version>5.3.2</version>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>