diff --git a/aws_lambda_powertools/utilities/feature_flags/feature_flags.py b/aws_lambda_powertools/utilities/feature_flags/feature_flags.py
index 3d913de98d4..1606933bbc2 100644
--- a/aws_lambda_powertools/utilities/feature_flags/feature_flags.py
+++ b/aws_lambda_powertools/utilities/feature_flags/feature_flags.py
@@ -46,7 +46,8 @@ def _match_by_action(action: str, condition_value: Any, context_value: Any) -> b
             schema.RuleAction.EQUALS.value: lambda a, b: a == b,
             schema.RuleAction.STARTSWITH.value: lambda a, b: a.startswith(b),
             schema.RuleAction.ENDSWITH.value: lambda a, b: a.endswith(b),
-            schema.RuleAction.CONTAINS.value: lambda a, b: a in b,
+            schema.RuleAction.IN.value: lambda a, b: a in b,
+            schema.RuleAction.NOT_IN.value: lambda a, b: a not in b,
         }
 
         try:
diff --git a/aws_lambda_powertools/utilities/feature_flags/schema.py b/aws_lambda_powertools/utilities/feature_flags/schema.py
index 6f2d2bf713c..efce82018db 100644
--- a/aws_lambda_powertools/utilities/feature_flags/schema.py
+++ b/aws_lambda_powertools/utilities/feature_flags/schema.py
@@ -20,7 +20,8 @@ class RuleAction(str, Enum):
     EQUALS = "EQUALS"
     STARTSWITH = "STARTSWITH"
     ENDSWITH = "ENDSWITH"
-    CONTAINS = "CONTAINS"
+    IN = "IN"
+    NOT_IN = "NOT_IN"
 
 
 class SchemaValidator(BaseValidator):
@@ -79,7 +80,7 @@ class SchemaValidator(BaseValidator):
     The value MUST contain the following members:
 
     * **action**: `str`. Operation to perform to match a key and value.
-    The value MUST be either EQUALS, STARTSWITH, ENDSWITH, CONTAINS
+    The value MUST be either EQUALS, STARTSWITH, ENDSWITH, IN, NOT_IN
     * **key**: `str`. Key in given context to perform operation
     * **value**: `Any`. Value in given context that should match action operation.
 
diff --git a/tests/functional/feature_flags/test_feature_flags.py b/tests/functional/feature_flags/test_feature_flags.py
index d2150268062..c0f463c78d0 100644
--- a/tests/functional/feature_flags/test_feature_flags.py
+++ b/tests/functional/feature_flags/test_feature_flags.py
@@ -263,7 +263,7 @@ def test_flags_conditions_rule_match_multiple_actions_multiple_rules_multiple_co
 
 
 # check a case where the feature exists but the rule doesn't match so we revert to the default value of the feature
-def test_flags_match_rule_with_contains_action(mocker, config):
+def test_flags_match_rule_with_in_action(mocker, config):
     expected_value = True
     mocked_app_config_schema = {
         "my_feature": {
@@ -273,7 +273,7 @@ def test_flags_match_rule_with_contains_action(mocker, config):
                     "when_match": expected_value,
                     "conditions": [
                         {
-                            "action": RuleAction.CONTAINS.value,
+                            "action": RuleAction.IN.value,
                             "key": "tenant_id",
                             "value": ["6", "2"],
                         }
@@ -287,7 +287,7 @@ def test_flags_match_rule_with_contains_action(mocker, config):
     assert toggle == expected_value
 
 
-def test_flags_no_match_rule_with_contains_action(mocker, config):
+def test_flags_no_match_rule_with_in_action(mocker, config):
     expected_value = False
     mocked_app_config_schema = {
         "my_feature": {
@@ -297,7 +297,7 @@ def test_flags_no_match_rule_with_contains_action(mocker, config):
                     "when_match": True,
                     "conditions": [
                         {
-                            "action": RuleAction.CONTAINS.value,
+                            "action": RuleAction.IN.value,
                             "key": "tenant_id",
                             "value": ["8", "2"],
                         }
@@ -311,6 +311,54 @@ def test_flags_no_match_rule_with_contains_action(mocker, config):
     assert toggle == expected_value
 
 
+def test_flags_match_rule_with_not_in_action(mocker, config):
+    expected_value = True
+    mocked_app_config_schema = {
+        "my_feature": {
+            "default": False,
+            "rules": {
+                "tenant id is contained in [8, 2]": {
+                    "when_match": expected_value,
+                    "conditions": [
+                        {
+                            "action": RuleAction.NOT_IN.value,
+                            "key": "tenant_id",
+                            "value": ["10", "4"],
+                        }
+                    ],
+                }
+            },
+        }
+    }
+    feature_flags = init_feature_flags(mocker, mocked_app_config_schema, config)
+    toggle = feature_flags.evaluate(name="my_feature", context={"tenant_id": "6", "username": "a"}, default=False)
+    assert toggle == expected_value
+
+
+def test_flags_no_match_rule_with_not_in_action(mocker, config):
+    expected_value = False
+    mocked_app_config_schema = {
+        "my_feature": {
+            "default": expected_value,
+            "rules": {
+                "tenant id is contained in [8, 2]": {
+                    "when_match": True,
+                    "conditions": [
+                        {
+                            "action": RuleAction.NOT_IN.value,
+                            "key": "tenant_id",
+                            "value": ["6", "4"],
+                        }
+                    ],
+                }
+            },
+        }
+    }
+    feature_flags = init_feature_flags(mocker, mocked_app_config_schema, config)
+    toggle = feature_flags.evaluate(name="my_feature", context={"tenant_id": "6", "username": "a"}, default=False)
+    assert toggle == expected_value
+
+
 def test_multiple_features_enabled(mocker, config):
     expected_value = ["my_feature", "my_feature2"]
     mocked_app_config_schema = {
@@ -321,7 +369,7 @@ def test_multiple_features_enabled(mocker, config):
                     "when_match": True,
                     "conditions": [
                         {
-                            "action": RuleAction.CONTAINS.value,
+                            "action": RuleAction.IN.value,
                             "key": "tenant_id",
                             "value": ["6", "2"],
                         }
@@ -351,7 +399,7 @@ def test_multiple_features_only_some_enabled(mocker, config):
                     "when_match": True,
                     "conditions": [
                         {
-                            "action": RuleAction.CONTAINS.value,
+                            "action": RuleAction.IN.value,
                             "key": "tenant_id",
                             "value": ["6", "2"],
                         }
@@ -464,7 +512,7 @@ def test_features_jmespath_envelope(mocker, config):
     assert toggle == expected_value
 
 
-# test_match_rule_with_contains_action
+# test_match_rule_with_equals_action
 def test_match_condition_with_dict_value(mocker, config):
     expected_value = True
     mocked_app_config_schema = {
diff --git a/tests/functional/feature_flags/test_schema_validation.py b/tests/functional/feature_flags/test_schema_validation.py
index 2c33d3c61cc..ce85494afce 100644
--- a/tests/functional/feature_flags/test_schema_validation.py
+++ b/tests/functional/feature_flags/test_schema_validation.py
@@ -211,10 +211,15 @@ def test_valid_condition_all_actions():
                             CONDITION_VALUE: "a",
                         },
                         {
-                            CONDITION_ACTION: RuleAction.CONTAINS.value,
+                            CONDITION_ACTION: RuleAction.IN.value,
                             CONDITION_KEY: "username",
                             CONDITION_VALUE: ["a", "b"],
                         },
+                        {
+                            CONDITION_ACTION: RuleAction.NOT_IN.value,
+                            CONDITION_KEY: "username",
+                            CONDITION_VALUE: ["c"],
+                        },
                     ],
                 }
             },