diff --git a/homeassistant/helpers/json.py b/homeassistant/helpers/json.py
index dbe3163da08..8b91f5eb2b5 100644
--- a/homeassistant/helpers/json.py
+++ b/homeassistant/helpers/json.py
@@ -35,6 +35,8 @@ def json_encoder_default(obj: Any) -> Any:
     """
     if isinstance(obj, set):
         return list(obj)
+    if isinstance(obj, float):
+        return float(obj)
     if hasattr(obj, "as_dict"):
         return obj.as_dict()
     if isinstance(obj, Path):
diff --git a/tests/helpers/test_json.py b/tests/helpers/test_json.py
index 17066b682af..cfb403ca4a9 100644
--- a/tests/helpers/test_json.py
+++ b/tests/helpers/test_json.py
@@ -8,6 +8,7 @@ from homeassistant import core
 from homeassistant.helpers.json import (
     ExtendedJSONEncoder,
     JSONEncoder,
+    json_dumps,
     json_dumps_sorted,
 )
 from homeassistant.util import dt as dt_util
@@ -77,3 +78,12 @@ def test_json_dumps_sorted():
     assert json_dumps_sorted(data) == json.dumps(
         data, sort_keys=True, separators=(",", ":")
     )
+
+
+def test_json_dumps_float_subclass():
+    """Test the json dumps a float subclass."""
+
+    class FloatSubclass(float):
+        """A float subclass."""
+
+    assert json_dumps({"c": FloatSubclass(1.2)}) == '{"c":1.2}'