diff --git a/aws_lambda_powertools/utilities/data_classes/alb_event.py b/aws_lambda_powertools/utilities/data_classes/alb_event.py
index 7d1541455d5..b9525e6a9f0 100644
--- a/aws_lambda_powertools/utilities/data_classes/alb_event.py
+++ b/aws_lambda_powertools/utilities/data_classes/alb_event.py
@@ -44,7 +44,17 @@ def request_context(self) -> ALBEventRequestContext:
 
     @property
     def resolved_query_string_parameters(self) -> dict[str, list[str]]:
-        params = self.multi_value_query_string_parameters or super().resolved_query_string_parameters
+        multi_value = self.multi_value_query_string_parameters
+        single_value = super().resolved_query_string_parameters
+
+        if not multi_value:
+            params = single_value
+        elif not single_value:
+            params = multi_value
+        else:
+            # Merge both: multi_value takes precedence, single_value fills missing keys
+            params = {**single_value, **multi_value}
+
         if not self.decode_query_parameters:
             return params
 
diff --git a/aws_lambda_powertools/utilities/data_classes/api_gateway_proxy_event.py b/aws_lambda_powertools/utilities/data_classes/api_gateway_proxy_event.py
index 6e24873e6d7..88f6cb8fa54 100644
--- a/aws_lambda_powertools/utilities/data_classes/api_gateway_proxy_event.py
+++ b/aws_lambda_powertools/utilities/data_classes/api_gateway_proxy_event.py
@@ -120,7 +120,17 @@ def multi_value_headers(self) -> dict[str, list[str]]:
 
     @property
     def resolved_query_string_parameters(self) -> dict[str, list[str]]:
-        return self.multi_value_query_string_parameters or super().resolved_query_string_parameters
+        multi_value = self.multi_value_query_string_parameters
+        single_value = super().resolved_query_string_parameters
+
+        if not multi_value:
+            return single_value
+
+        if not single_value:
+            return multi_value
+
+        # Merge both: multi_value takes precedence, single_value fills missing keys
+        return {**single_value, **multi_value}
 
     @property
     def resolved_headers_field(self) -> dict[str, Any]:
diff --git a/tests/unit/data_classes/required_dependencies/test_alb_event.py b/tests/unit/data_classes/required_dependencies/test_alb_event.py
index 13d8b5907be..23ab7af6365 100644
--- a/tests/unit/data_classes/required_dependencies/test_alb_event.py
+++ b/tests/unit/data_classes/required_dependencies/test_alb_event.py
@@ -52,3 +52,17 @@ def test_alb_event_decode_multi_value_query_parameters():
     # With decode_query_parameters, the key and value are not decoded
     parsed_event.decode_query_parameters = True
     assert parsed_event.resolved_query_string_parameters == {expected_key: expected_values}
+
+
+def test_alb_event_merged_query_string_parameters():
+    """When both multiValueQueryStringParameters and queryStringParameters are present,
+    resolved_query_string_parameters should merge them (GH #7993)."""
+    raw_event = load_event("albMultiValueQueryStringEvent.json")
+    raw_event["multiValueQueryStringParameters"] = {"ids": ["1", "2", "3"]}
+    raw_event["queryStringParameters"] = {"status": "fizzbuzz"}
+
+    parsed_event = ALBEvent(raw_event)
+    resolved = parsed_event.resolved_query_string_parameters
+
+    assert resolved["ids"] == ["1", "2", "3"]
+    assert resolved["status"] == ["fizzbuzz"]
diff --git a/tests/unit/data_classes/required_dependencies/test_api_gateway_proxy_event.py b/tests/unit/data_classes/required_dependencies/test_api_gateway_proxy_event.py
index ec71d815a7c..fd9ca1cca76 100644
--- a/tests/unit/data_classes/required_dependencies/test_api_gateway_proxy_event.py
+++ b/tests/unit/data_classes/required_dependencies/test_api_gateway_proxy_event.py
@@ -241,3 +241,53 @@ def test_api_gateway_proxy_v2_iam_event():
     assert iam.principal_org_id == iam_raw["principalOrgId"]
     assert iam.user_arn == iam_raw["userArn"]
     assert iam.user_id == iam_raw["userId"]
+
+
+def test_api_gateway_proxy_event_merged_query_string_parameters():
+    """When both multiValueQueryStringParameters and queryStringParameters are present,
+    resolved_query_string_parameters should merge them (GH #7993)."""
+    raw_event = load_event("apiGatewayProxyEvent.json")
+    raw_event["multiValueQueryStringParameters"] = {"ids": ["1", "2", "3"]}
+    raw_event["queryStringParameters"] = {"status": "fizzbuzz"}
+
+    parsed_event = APIGatewayProxyEvent(raw_event)
+    resolved = parsed_event.resolved_query_string_parameters
+
+    assert resolved["ids"] == ["1", "2", "3"]
+    assert resolved["status"] == ["fizzbuzz"]
+
+
+def test_api_gateway_proxy_event_multi_value_takes_precedence():
+    """When the same key exists in both, multiValueQueryStringParameters wins."""
+    raw_event = load_event("apiGatewayProxyEvent.json")
+    raw_event["multiValueQueryStringParameters"] = {"key": ["a", "b"]}
+    raw_event["queryStringParameters"] = {"key": "c"}
+
+    parsed_event = APIGatewayProxyEvent(raw_event)
+    resolved = parsed_event.resolved_query_string_parameters
+
+    assert resolved["key"] == ["a", "b"]
+
+
+def test_api_gateway_proxy_event_only_single_value_query_params():
+    """When only queryStringParameters is present, it should still work."""
+    raw_event = load_event("apiGatewayProxyEvent.json")
+    raw_event["multiValueQueryStringParameters"] = None
+    raw_event["queryStringParameters"] = {"status": "active"}
+
+    parsed_event = APIGatewayProxyEvent(raw_event)
+    resolved = parsed_event.resolved_query_string_parameters
+
+    assert resolved["status"] == ["active"]
+
+
+def test_api_gateway_proxy_event_only_multi_value_query_params():
+    """When only multiValueQueryStringParameters is present, it should still work."""
+    raw_event = load_event("apiGatewayProxyEvent.json")
+    raw_event["multiValueQueryStringParameters"] = {"ids": ["1", "2"]}
+    raw_event["queryStringParameters"] = None
+
+    parsed_event = APIGatewayProxyEvent(raw_event)
+    resolved = parsed_event.resolved_query_string_parameters
+
+    assert resolved["ids"] == ["1", "2"]