diff --git a/.changes/1021e75a-45f3-4f3a-820c-700d9ec6e782.json b/.changes/1021e75a-45f3-4f3a-820c-700d9ec6e782.json
new file mode 100644
index 0000000000..0fad5e0349
--- /dev/null
+++ b/.changes/1021e75a-45f3-4f3a-820c-700d9ec6e782.json
@@ -0,0 +1,5 @@
+{
+    "id": "1021e75a-45f3-4f3a-820c-700d9ec6e782",
+    "type": "bugfix",
+    "description": "Fix serialization of CBOR blobs"
+}
\ No newline at end of file
diff --git a/codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/protocol/HttpProtocolUnitTestRequestGenerator.kt b/codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/protocol/HttpProtocolUnitTestRequestGenerator.kt
index 74bd7db782..6fcc47c3e5 100644
--- a/codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/protocol/HttpProtocolUnitTestRequestGenerator.kt
+++ b/codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/protocol/HttpProtocolUnitTestRequestGenerator.kt
@@ -117,11 +117,11 @@ open class HttpProtocolUnitTestRequestGenerator protected constructor(builder: B
                         write("return")
                     }
                     write("requireNotNull(expectedBytes) { #S }", "expected application/cbor body cannot be null")
-                    write("requireNotNull(expectedBytes) { #S }", "actual application/cbor body cannot be null")
+                    write("requireNotNull(actualBytes) { #S }", "actual application/cbor body cannot be null")
 
                     write("")
                     write("val expectedRequest = #L(#T(expectedBytes))", inputDeserializer.name, RuntimeTypes.Serde.SerdeCbor.CborDeserializer)
-                    write("val actualRequest = #L(#T(expectedBytes))", inputDeserializer.name, RuntimeTypes.Serde.SerdeCbor.CborDeserializer)
+                    write("val actualRequest = #L(#T(actualBytes))", inputDeserializer.name, RuntimeTypes.Serde.SerdeCbor.CborDeserializer)
                     write("assertEquals(expectedRequest, actualRequest)")
                 }
                 writer.write("")
diff --git a/codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/SerializeStructGenerator.kt b/codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/SerializeStructGenerator.kt
index e7f2e261ef..d8810044a5 100644
--- a/codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/SerializeStructGenerator.kt
+++ b/codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/SerializeStructGenerator.kt
@@ -647,7 +647,6 @@ open class SerializeStructGenerator(
         val target = member.targetOrSelf(ctx.model)
 
         val encoded = when {
-            target.type == ShapeType.BLOB -> writer.format("#L.#T()", identifier, RuntimeTypes.Core.Text.Encoding.encodeBase64String)
             target.type == ShapeType.TIMESTAMP -> {
                 writer.addImport(RuntimeTypes.Core.TimestampFormat)
                 val tsFormat = member
diff --git a/codegen/smithy-kotlin-codegen/src/test/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/SerializeStructGeneratorTest.kt b/codegen/smithy-kotlin-codegen/src/test/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/SerializeStructGeneratorTest.kt
index 40d9c9db7d..347da007cb 100644
--- a/codegen/smithy-kotlin-codegen/src/test/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/SerializeStructGeneratorTest.kt
+++ b/codegen/smithy-kotlin-codegen/src/test/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/SerializeStructGeneratorTest.kt
@@ -1822,7 +1822,7 @@ class SerializeStructGeneratorTest {
 
         val expected = """
             serializer.serializeStruct(OBJ_DESCRIPTOR) {
-                input.fooBlob?.let { field(FOOBLOB_DESCRIPTOR, it.encodeBase64String()) }
+                input.fooBlob?.let { field(FOOBLOB_DESCRIPTOR, it) }
             }
         """.trimIndent()
 
diff --git a/runtime/serde/serde-xml/common/src/aws/smithy/kotlin/runtime/serde/xml/XmlSerializer.kt b/runtime/serde/serde-xml/common/src/aws/smithy/kotlin/runtime/serde/xml/XmlSerializer.kt
index 35618cb49e..d1356f848c 100644
--- a/runtime/serde/serde-xml/common/src/aws/smithy/kotlin/runtime/serde/xml/XmlSerializer.kt
+++ b/runtime/serde/serde-xml/common/src/aws/smithy/kotlin/runtime/serde/xml/XmlSerializer.kt
@@ -134,7 +134,7 @@ public class XmlSerializer(private val xmlWriter: XmlStreamWriter = xmlStreamWri
         field(descriptor, value.format(format))
 
     override fun field(descriptor: SdkFieldDescriptor, value: ByteArray): Unit =
-        field(descriptor, value)
+        field(descriptor, value.encodeBase64String())
 
     override fun field(descriptor: SdkFieldDescriptor, value: Document?): Unit = throw SerializationException(
         "cannot serialize field ${descriptor.serialName}; Document type is not supported by xml encoding",