diff --git a/.brazil.json b/.brazil.json
index 1c03434718..518ff56948 100644
--- a/.brazil.json
+++ b/.brazil.json
@@ -1,7 +1,7 @@
 {
   "dependencies": {
     "org.jetbrains.kotlin:kotlin-stdlib:2.0.*": "KotlinStdlib-2.x",
-    "org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.8.*": "KotlinxCoroutinesCoreJvm-1.8.x",
+    "org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.*": "KotlinxCoroutinesCoreJvm-1.x",
 
     "com.squareup.okhttp3:okhttp-coroutines:5.*": "OkHttp3Coroutines-5.x",
     "com.squareup.okhttp3:okhttp:5.*": "OkHttp3-5.x",
@@ -34,7 +34,7 @@
     "resolvesConflictDependencies": {
       "com.squareup.okhttp3:okhttp-coroutines:5.*": [
         "KotlinStdlib-2.x",
-        "KotlinxCoroutinesCoreJvm-1.8.x",
+        "KotlinxCoroutinesCoreJvm-1.x",
         "KotlinStdlibJdk7-2.x",
         "KotlinStdlibJdk8-2.x"
       ],
diff --git a/.changes/347d905e-25a5-49be-9d32-4fbf9305e85d.json b/.changes/347d905e-25a5-49be-9d32-4fbf9305e85d.json
new file mode 100644
index 0000000000..467ac92590
--- /dev/null
+++ b/.changes/347d905e-25a5-49be-9d32-4fbf9305e85d.json
@@ -0,0 +1,5 @@
+{
+    "id": "347d905e-25a5-49be-9d32-4fbf9305e85d",
+    "type": "misc",
+    "description": "Upgrade to kotlinx.coroutines 1.9.0"
+}
\ No newline at end of file
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 6f8da90162..3dd88c2cb1 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -5,7 +5,7 @@ dokka-version = "1.9.10"
 aws-kotlin-repo-tools-version = "0.4.10"
 
 # libs
-coroutines-version = "1.8.1"
+coroutines-version = "1.9.0"
 atomicfu-version = "0.24.0"
 okhttp-version = "5.0.0-alpha.14"
 okhttp4-version = "4.12.0"
@@ -13,7 +13,7 @@ okio-version = "3.9.0"
 otel-version = "1.32.0"
 slf4j-version = "2.0.9"
 slf4j-v1x-version = "1.7.36"
-crt-kotlin-version = "0.8.8"
+crt-kotlin-version = "0.8.9"
 micrometer-version = "1.13.2"
 
 # codegen
diff --git a/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/retries/delay/StandardRetryTokenBucketTest.kt b/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/retries/delay/StandardRetryTokenBucketTest.kt
index 4f89375ead..d540535792 100644
--- a/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/retries/delay/StandardRetryTokenBucketTest.kt
+++ b/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/retries/delay/StandardRetryTokenBucketTest.kt
@@ -15,7 +15,6 @@ import kotlin.test.assertEquals
 import kotlin.test.assertIs
 import kotlin.time.Duration.Companion.milliseconds
 import kotlin.time.Duration.Companion.seconds
-import kotlin.time.ExperimentalTime
 import kotlin.time.TestTimeSource
 import kotlin.time.TimeSource
 
@@ -107,7 +106,7 @@ class StandardRetryTokenBucketTest {
     }
 }
 
-@OptIn(ExperimentalCoroutinesApi::class, ExperimentalTime::class)
+@OptIn(ExperimentalCoroutinesApi::class)
 private fun TestScope.tokenBucket(
     useCircuitBreakerMode: Boolean = false,
     initialTryCost: Int = 0,
diff --git a/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/retries/delay/TimingUtils.kt b/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/retries/delay/TimingUtils.kt
index 702978d9bd..61dbad3bc8 100644
--- a/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/retries/delay/TimingUtils.kt
+++ b/runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/retries/delay/TimingUtils.kt
@@ -11,10 +11,9 @@ import kotlinx.coroutines.test.currentTime
 import kotlinx.coroutines.test.testTimeSource
 import kotlin.test.assertEquals
 import kotlin.time.Duration
-import kotlin.time.ExperimentalTime
 import kotlin.time.measureTimedValue
 
-@OptIn(ExperimentalCoroutinesApi::class, ExperimentalTime::class)
+@OptIn(ExperimentalCoroutinesApi::class)
 suspend fun <T> TestScope.assertTime(expectedDuration: Duration, block: suspend () -> T): T {
     val (result, actualDuration) = testTimeSource.measureTimedValue { block() }
 
diff --git a/runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/retries/impl/AdaptiveRetryIntegrationTest.kt b/runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/retries/impl/AdaptiveRetryIntegrationTest.kt
index 7775088465..77425afd1c 100644
--- a/runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/retries/impl/AdaptiveRetryIntegrationTest.kt
+++ b/runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/retries/impl/AdaptiveRetryIntegrationTest.kt
@@ -14,11 +14,10 @@ import kotlinx.coroutines.test.testTimeSource
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.time.Duration.Companion.seconds
-import kotlin.time.ExperimentalTime
 
 private const val TOLERANCE = 0.0000005
 
-@OptIn(ExperimentalTime::class, ExperimentalCoroutinesApi::class)
+@OptIn(ExperimentalCoroutinesApi::class)
 class AdaptiveRetryIntegrationTest {
     @Test
     fun testCubicCases() = runTest {