diff --git a/docs/changelog/3534.feature.rst b/docs/changelog/3534.feature.rst
new file mode 100644
index 0000000000..fb283a62f6
--- /dev/null
+++ b/docs/changelog/3534.feature.rst
@@ -0,0 +1 @@
+Add ``free_threaded`` flag to to ``"python"`` entries in json output of ``--result-json``.
diff --git a/src/tox/tox_env/python/api.py b/src/tox/tox_env/python/api.py
index db59259fbf..ae0375904c 100644
--- a/src/tox/tox_env/python/api.py
+++ b/src/tox/tox_env/python/api.py
@@ -312,6 +312,7 @@ def _get_env_journal_python(self) -> dict[str, Any]:
             "is_64": self.base_python.is_64,
             "sysplatform": self.base_python.platform,
             "extra_version_info": None,
+            "free_threaded": self.base_python.free_threaded,
         }
 
     @abstractmethod
diff --git a/tests/session/cmd/test_sequential.py b/tests/session/cmd/test_sequential.py
index 87771be037..1bd0f1fd30 100644
--- a/tests/session/cmd/test_sequential.py
+++ b/tests/session/cmd/test_sequential.py
@@ -89,6 +89,7 @@ def test_result_json_sequential(
         "sysplatform": py_info.platform,
         "version": py_info.version,
         "version_info": list(py_info.version_info),
+        "free_threaded": py_info.free_threaded,
     }
     packaging_setup = get_cmd_exit_run_id(log_report, ".pkg", "setup")
     assert "result" not in log_report["testenvs"][".pkg"]