diff --git a/.changes/next-release/bugfix-AWSCRTbasedS3Client-7a3c1e2.json b/.changes/next-release/bugfix-AWSCRTbasedS3Client-7a3c1e2.json
new file mode 100644
index 000000000000..78233be09295
--- /dev/null
+++ b/.changes/next-release/bugfix-AWSCRTbasedS3Client-7a3c1e2.json
@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "AWS CRT-based S3 Client",
+    "contributor": "MingWangSong",
+    "description": "Fixed an issue where the CRT-based S3 client always established proxy connections through a `CONNECT` tunnel, even when `endpointOverride` used the plaintext `http://` scheme. Proxies that only support forwarding mode rejected these requests. The proxy connection type is now pinned to forwarding for plaintext endpoints, matching the behavior of `ApacheHttpClient`. See [#7320](https://github.com/aws/aws-sdk-java-v2/issues/7320)."
+}
diff --git a/services/s3/src/main/java/software/amazon/awssdk/services/s3/internal/crt/S3NativeClientConfiguration.java b/services/s3/src/main/java/software/amazon/awssdk/services/s3/internal/crt/S3NativeClientConfiguration.java
index b3c0742a272c..47b428699dcc 100644
--- a/services/s3/src/main/java/software/amazon/awssdk/services/s3/internal/crt/S3NativeClientConfiguration.java
+++ b/services/s3/src/main/java/software/amazon/awssdk/services/s3/internal/crt/S3NativeClientConfiguration.java
@@ -47,6 +47,7 @@ public class S3NativeClientConfiguration implements SdkAutoCloseable {
     static final long DEFAULT_PART_SIZE_IN_BYTES = 8L * 1024 * 1024;
     private static final Logger log = Logger.loggerFor(S3NativeClientConfiguration.class);
     private static final long DEFAULT_TARGET_THROUGHPUT_IN_GBPS = 10;
+    private static final String HTTP_SCHEME = "http";
 
     private final String signingRegion;
     private final StandardRetryOptions standardRetryOptions;
@@ -106,6 +107,7 @@ public S3NativeClientConfiguration(Builder builder) {
 
         if (builder.httpConfiguration != null) {
             this.proxyOptions = resolveProxy(builder.httpConfiguration.proxyConfiguration(), tlsContext).orElse(null);
+            applyPlaintextEndpointProxyConnectionType(this.proxyOptions, this.endpointOverride);
             this.connectionTimeout = builder.httpConfiguration.connectionTimeout();
             this.httpMonitoringOptions =
                 resolveHttpMonitoringOptions(builder.httpConfiguration.healthConfiguration()).orElse(null);
@@ -135,6 +137,24 @@ private long resolveThresholdInBytes(Builder builder) {
         return this.partSizeInBytes == null ? DEFAULT_PART_SIZE_IN_BYTES : this.partSizeInBytes;
     }
 
+    /**
+     * Pins the proxy connection type to forwarding when the endpoint is plaintext.
+     *
+     * <p>The CRT derives the proxy connection type from whether TLS options were supplied for the main connection,
+     * not from the scheme actually in use. Because this client is always constructed with a {@link TlsContext}, a
+     * plaintext {@code http://} endpoint would otherwise be reached through a {@code CONNECT} tunnel, which
+     * forwarding-only proxies reject. This mirrors the scheme check that the CRT's own
+     * {@code HttpClientConnectionManager} performs before handing a TLS context to the native layer.
+     */
+    private static void applyPlaintextEndpointProxyConnectionType(HttpProxyOptions proxyOptions, URI endpointOverride) {
+        if (proxyOptions == null || endpointOverride == null) {
+            return;
+        }
+        if (HTTP_SCHEME.equalsIgnoreCase(endpointOverride.getScheme())) {
+            proxyOptions.setConnectionType(HttpProxyOptions.HttpProxyConnectionType.Forwarding);
+        }
+    }
+
     private static Boolean resolveUseEnvironmentVariableValues(Builder builder) {
         if (builder != null && builder.httpConfiguration != null && builder.httpConfiguration.proxyConfiguration() != null) {
             return builder.httpConfiguration.proxyConfiguration().isUseEnvironmentVariableValues();
diff --git a/services/s3/src/test/java/software/amazon/awssdk/services/s3/internal/crt/S3NativeClientConfigurationTest.java b/services/s3/src/test/java/software/amazon/awssdk/services/s3/internal/crt/S3NativeClientConfigurationTest.java
index 0fdb91c0e6a5..5662d6b8237c 100644
--- a/services/s3/src/test/java/software/amazon/awssdk/services/s3/internal/crt/S3NativeClientConfigurationTest.java
+++ b/services/s3/src/test/java/software/amazon/awssdk/services/s3/internal/crt/S3NativeClientConfigurationTest.java
@@ -17,6 +17,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import java.net.URI;
 import java.util.stream.Stream;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -24,6 +25,8 @@
 import org.junit.jupiter.params.provider.MethodSource;
 import software.amazon.awssdk.auth.credentials.AwsBasicCredentials;
 import software.amazon.awssdk.auth.credentials.StaticCredentialsProvider;
+import software.amazon.awssdk.crt.http.HttpProxyOptions;
+import software.amazon.awssdk.services.s3.crt.S3CrtProxyConfiguration;
 import software.amazon.awssdk.services.s3.crt.S3CrtHttpConfiguration;
 import software.amazon.awssdk.testutils.LogCaptor;
 
@@ -61,7 +64,49 @@ private static Stream<Arguments> noWarningConfigurations() {
         );
     }
 
+    @ParameterizedTest
+    @MethodSource("proxyConnectionTypeCases")
+    void build_proxyConnectionType_followsEndpointScheme(URI endpointOverride,
+                                                         HttpProxyOptions.HttpProxyConnectionType expectedType) {
+        S3CrtHttpConfiguration httpConfig =
+            S3CrtHttpConfiguration.builder()
+                                  .proxyConfiguration(S3CrtProxyConfiguration.builder()
+                                                                             .scheme("http")
+                                                                             .host("localhost")
+                                                                             .port(8888)
+                                                                             .build())
+                                  .build();
+
+        try (S3NativeClientConfiguration config = buildConfig(httpConfig, endpointOverride)) {
+            assertThat(config.proxyOptions().getConnectionType()).isEqualTo(expectedType);
+        }
+    }
+
+    private static Stream<Arguments> proxyConnectionTypeCases() {
+        return Stream.of(
+            Arguments.of(URI.create("http://localhost:9000"),
+                         HttpProxyOptions.HttpProxyConnectionType.Forwarding),
+            Arguments.of(URI.create("HTTP://localhost:9000"),
+                         HttpProxyOptions.HttpProxyConnectionType.Forwarding),
+            Arguments.of(URI.create("https://s3.us-east-1.amazonaws.com"),
+                         HttpProxyOptions.HttpProxyConnectionType.Legacy),
+            Arguments.of(null, HttpProxyOptions.HttpProxyConnectionType.Legacy)
+        );
+    }
+
+    @Test
+    void build_whenPlaintextEndpointAndNoProxy_shouldNotSetProxyOptions() {
+        try (S3NativeClientConfiguration config = buildConfig(S3CrtHttpConfiguration.builder().build(),
+                                                              URI.create("http://localhost:9000"))) {
+            assertThat(config.proxyOptions()).isNull();
+        }
+    }
+
     private S3NativeClientConfiguration buildConfig(S3CrtHttpConfiguration httpConfig) {
+        return buildConfig(httpConfig, null);
+    }
+
+    private S3NativeClientConfiguration buildConfig(S3CrtHttpConfiguration httpConfig, URI endpointOverride) {
         S3NativeClientConfiguration.Builder builder =
             S3NativeClientConfiguration.builder()
                                        .signingRegion("us-east-1")
@@ -71,6 +116,9 @@ private S3NativeClientConfiguration buildConfig(S3CrtHttpConfiguration httpConfi
         if (httpConfig != null) {
             builder.httpConfiguration(httpConfig);
         }
+        if (endpointOverride != null) {
+            builder.endpointOverride(endpointOverride);
+        }
         return builder.build();
     }
 }