diff --git a/moto/kms/models.py b/moto/kms/models.py
index 6c53dad06..a1971a05c 100644
--- a/moto/kms/models.py
+++ b/moto/kms/models.py
@@ -22,6 +22,7 @@ from .utils import (
     generate_key_id,
     generate_master_key,
     generate_private_key,
+    KeySpec,
 )
 
 
@@ -302,6 +303,8 @@ class KmsBackend(BaseBackend):
          - The resource is set to "*"
          - The Action matches `describe_key`
         """
+        if key_spec:
+            self.__ensure_valid_key_spec(key_spec)
         key = Key(
             policy,
             key_usage,
@@ -615,6 +618,16 @@ class KmsBackend(BaseBackend):
                 )
             )
 
+    def __ensure_valid_key_spec(self, key_spec: str) -> None:
+        if key_spec not in KeySpec.key_specs():
+            raise ValidationException(
+                (
+                    "1 validation error detected: Value '{key_spec}' at 'KeySpec' failed "
+                    "to satisfy constraint: Member must satisfy enum value set: "
+                    "{valid_key_specs}"
+                ).format(key_spec=key_spec, valid_key_specs=KeySpec.key_specs())
+            )
+
     def sign(
         self, key_id: str, message: bytes, signing_algorithm: str
     ) -> Tuple[str, bytes, str]:
diff --git a/moto/kms/utils.py b/moto/kms/utils.py
index 2639f5ca4..35fec1c0f 100644
--- a/moto/kms/utils.py
+++ b/moto/kms/utils.py
@@ -1,5 +1,6 @@
 from collections import namedtuple
-from typing import Any, Dict, Tuple
+from typing import Any, Dict, Tuple, List
+from enum import Enum
 import io
 import os
 import struct
@@ -48,6 +49,28 @@ RESERVED_ALIASE_TARGET_KEY_IDS = {
 RESERVED_ALIASES = list(RESERVED_ALIASE_TARGET_KEY_IDS.keys())
 
 
+class KeySpec(str, Enum):
+    # Asymmetric key specs
+    RSA_2048 = "RSA_2048"
+    RSA_3072 = "RSA_3072"
+    RSA_4096 = "RSA_4096"
+    ECC_NIST_P256 = "ECC_NIST_P256"
+    ECC_SECG_P256K1 = "ECC_SECG_P256K1"
+    ECC_NIST_P384 = "ECC_NIST_P384"
+    ECC_NIST_P512 = "ECC_NIST_P521"
+    SM2 = "SM2"  # China Regions only
+    # Symmetric key specs
+    SYMMETRIC_DEFAULT = "SYMMETRIC_DEFAULT"
+    HMAC_224 = "HMAC_224"
+    HMAC_256 = "HMAC_256"
+    HMAC_284 = "HMAC_384"
+    HMAC_512 = "HMAC_512"
+
+    @classmethod
+    def key_specs(self) -> List[str]:
+        return sorted([item.value for item in KeySpec])
+
+
 def generate_key_id(multi_region: bool = False) -> str:
     key = str(mock_random.uuid4())
     # https://docs.aws.amazon.com/kms/latest/developerguide/multi-region-keys-overview.html
diff --git a/tests/test_kms/test_kms_boto3.py b/tests/test_kms/test_kms_boto3.py
index dd82e9c2c..3c1e0ab8d 100644
--- a/tests/test_kms/test_kms_boto3.py
+++ b/tests/test_kms/test_kms_boto3.py
@@ -42,6 +42,21 @@ def test_create_key_without_description():
     assert metadata["Description"] == ""
 
 
+@mock_kms
+def test_create_key_with_invalid_key_spec():
+    conn = boto3.client("kms", region_name="us-east-1")
+    unsupported_key_spec = "NotSupportedKeySpec"
+    with pytest.raises(ClientError) as ex:
+        conn.create_key(Policy="my policy", KeySpec=unsupported_key_spec)
+    err = ex.value.response["Error"]
+    assert err["Code"] == "ValidationException"
+    assert err["Message"] == (
+        "1 validation error detected: Value '{key_spec}' at 'KeySpec' failed "
+        "to satisfy constraint: Member must satisfy enum value set: "
+        "['ECC_NIST_P256', 'ECC_NIST_P384', 'ECC_NIST_P521', 'ECC_SECG_P256K1', 'HMAC_224', 'HMAC_256', 'HMAC_384', 'HMAC_512', 'RSA_2048', 'RSA_3072', 'RSA_4096', 'SM2', 'SYMMETRIC_DEFAULT']"
+    ).format(key_spec=unsupported_key_spec)
+
+
 @mock_kms
 def test_create_key():
     conn = boto3.client("kms", region_name="us-east-1")