diff --git a/.changes/next-release/bugfix-AWSSDKforJavav2-3312616.json b/.changes/next-release/bugfix-AWSSDKforJavav2-3312616.json
new file mode 100644
index 000000000000..cdfb6f4f97d9
--- /dev/null
+++ b/.changes/next-release/bugfix-AWSSDKforJavav2-3312616.json
@@ -0,0 +1,6 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "contributor": "", 
+    "type": "bugfix", 
+    "description": "Update Sigv4a signer to include the port in the Host header, when the port does not match the standard port for the protocol. This allows requests to endpoints with non-standard ports to succeed."
+}
diff --git a/core/auth-crt/src/main/java/software/amazon/awssdk/authcrt/signer/internal/SigningUtils.java b/core/auth-crt/src/main/java/software/amazon/awssdk/authcrt/signer/internal/SigningUtils.java
index 24cf1e0d98a5..6541997d5b32 100644
--- a/core/auth-crt/src/main/java/software/amazon/awssdk/authcrt/signer/internal/SigningUtils.java
+++ b/core/auth-crt/src/main/java/software/amazon/awssdk/authcrt/signer/internal/SigningUtils.java
@@ -15,8 +15,6 @@
 
 package software.amazon.awssdk.authcrt.signer.internal;
 
-import static software.amazon.awssdk.utils.CollectionUtils.isNullOrEmpty;
-
 import java.nio.charset.StandardCharsets;
 import java.time.Clock;
 import java.time.Duration;
@@ -35,6 +33,7 @@
 import software.amazon.awssdk.crt.auth.credentials.Credentials;
 import software.amazon.awssdk.http.SdkHttpFullRequest;
 import software.amazon.awssdk.utils.StringUtils;
+import software.amazon.awssdk.utils.http.SdkHttpUtils;
 
 @SdkInternalApi
 public class SigningUtils {
@@ -116,19 +115,19 @@ public static SdkHttpFullRequest sanitizeSdkRequestForCrtSigning(SdkHttpFullRequ
 
         builder.clearHeaders();
 
-        // Add host if missing
-        Map<String, List<String>> headers = request.headers();
-        if (isNullOrEmpty(headers.get(HOST_HEADER))) {
-            builder.putHeader(HOST_HEADER, request.host());
-        }
-
         // Filter headers that will cause signing to fail
-        for (Map.Entry<String, List<String>> header: headers.entrySet()) {
+        for (Map.Entry<String, List<String>> header: request.headers().entrySet()) {
             if (!FORBIDDEN_HEADERS.contains(header.getKey())) {
                 builder.putHeader(header.getKey(), header.getValue());
             }
         }
 
+        // Add host, which must be signed. We ignore any pre-existing Host header to match the behavior of the SigV4 signer.
+        String hostHeader = SdkHttpUtils.isUsingStandardPort(request.protocol(), request.port())
+                            ? request.host()
+                            : request.host() + ":" + request.port();
+        builder.putHeader(HOST_HEADER, hostHeader);
+
         builder.clearQueryParameters();
 
         // Filter query parameters that will cause signing to fail
diff --git a/core/auth-crt/src/test/java/software/amazon/awssdk/authcrt/signer/AwsCrtV4aSignerTest.java b/core/auth-crt/src/test/java/software/amazon/awssdk/authcrt/signer/AwsCrtV4aSignerTest.java
index 3b936d9cf7b5..59cb8235b429 100644
--- a/core/auth-crt/src/test/java/software/amazon/awssdk/authcrt/signer/AwsCrtV4aSignerTest.java
+++ b/core/auth-crt/src/test/java/software/amazon/awssdk/authcrt/signer/AwsCrtV4aSignerTest.java
@@ -44,6 +44,45 @@ public void setup() {
         v4aSigner = AwsCrtV4aSigner.create();
     }
 
+    @Test
+    public void hostHeaderExcludesStandardHttpPort() {
+        SigningTestCase testCase = SignerTestUtils.createBasicHeaderSigningTestCase();
+        ExecutionAttributes executionAttributes = SignerTestUtils.buildBasicExecutionAttributes(testCase);
+
+        SdkHttpFullRequest request = testCase.requestBuilder.protocol("http")
+                                                            .port(80)
+                                                            .build();
+        SdkHttpFullRequest signed = v4aSigner.sign(request, executionAttributes);
+
+        assertThat(signed.firstMatchingHeader("Host")).hasValue("demo.us-east-1.amazonaws.com");
+    }
+
+    @Test
+    public void hostHeaderExcludesStandardHttpsPort() {
+        SigningTestCase testCase = SignerTestUtils.createBasicHeaderSigningTestCase();
+        ExecutionAttributes executionAttributes = SignerTestUtils.buildBasicExecutionAttributes(testCase);
+
+        SdkHttpFullRequest request = testCase.requestBuilder.protocol("https")
+                                                            .port(443)
+                                                            .build();
+        SdkHttpFullRequest signed = v4aSigner.sign(request, executionAttributes);
+
+        assertThat(signed.firstMatchingHeader("Host")).hasValue("demo.us-east-1.amazonaws.com");
+    }
+
+    @Test
+    public void hostHeaderIncludesNonStandardPorts() {
+        SigningTestCase testCase = SignerTestUtils.createBasicHeaderSigningTestCase();
+        ExecutionAttributes executionAttributes = SignerTestUtils.buildBasicExecutionAttributes(testCase);
+
+        SdkHttpFullRequest request = testCase.requestBuilder.protocol("http")
+                                                            .port(443)
+                                                            .build();
+        SdkHttpFullRequest signed = v4aSigner.sign(request, executionAttributes);
+
+        assertThat(signed.firstMatchingHeader("Host")).hasValue("demo.us-east-1.amazonaws.com:443");
+    }
+
     @Test
     public void testHeaderSigning() {
         SigningTestCase testCase = SignerTestUtils.createBasicHeaderSigningTestCase();