diff --git a/tests/parser/test_chat_parsing.py b/tests/parser/test_chat_parsing.py
index 679d97f15b..e3b8dba172 100644
--- a/tests/parser/test_chat_parsing.py
+++ b/tests/parser/test_chat_parsing.py
@@ -1555,6 +1555,14 @@ class ToolArgCoercionTest(unittest.TestCase):
     def test_coerce_falls_back_to_raw_on_failure(self):
         self.assertEqual(_coerce("not-a-number", ("integer",)), "not-a-number")
 
+    def test_coerce_integer_accepts_whole_number_floats(self):
+        self.assertEqual(_coerce("3.0", ("integer",)), 3)
+        self.assertIsInstance(_coerce("3.0", ("integer",)), int)
+        self.assertEqual(_coerce("3.5", ("integer",)), "3.5")
+        self.assertEqual(_coerce("3.5", ("integer", "number")), 3.5)
+        self.assertEqual(_coerce("inf", ("integer",)), "inf")
+        self.assertEqual(_coerce("NaN", ("integer",)), "NaN")
+
     def test_coerce_handles_any_of_and_null(self):
         self.assertEqual(_coerce("5", ("integer", "null")), 5)
         self.assertIsNone(_coerce("null", ("integer", "null")))
diff --git a/vllm/parser/chat_parsing/response_parser.py b/vllm/parser/chat_parsing/response_parser.py
index 556df803a7..0416fe0fe3 100644
--- a/vllm/parser/chat_parsing/response_parser.py
+++ b/vllm/parser/chat_parsing/response_parser.py
@@ -50,7 +50,14 @@ def _coerce(raw: str, types: tuple[str, ...]) -> Any:
     for type_name in types:
         try:
             if type_name == "integer":
-                return int(raw)
+                try:
+                    return int(raw)
+                except ValueError:
+                    # JSON Schema integers include whole numbers written as floats, e.g. "3.0"
+                    number = float(raw)
+                    if not number.is_integer():
+                        continue
+                    return int(number)
             if type_name == "number":
                 number = float(raw)
                 if number != number or number in (float("inf"), float("-inf")):