diff --git a/homeassistant/helpers/config_validation.py b/homeassistant/helpers/config_validation.py
index 9be584403bd..e5b113f8a4d 100644
--- a/homeassistant/helpers/config_validation.py
+++ b/homeassistant/helpers/config_validation.py
@@ -86,7 +86,7 @@ import homeassistant.util.dt as dt_util
 
 # pylint: disable=invalid-name
 
-TIME_PERIOD_ERROR = "offset {} should be format 'HH:MM' or 'HH:MM:SS'"
+TIME_PERIOD_ERROR = "offset {} should be format 'HH:MM', 'HH:MM:SS' or 'HH:MM:SS.F'"
 
 # Home Assistant types
 byte = vol.All(vol.Coerce(int), vol.Range(min=0, max=255))
@@ -299,11 +299,11 @@ time_period_dict = vol.All(
     dict,
     vol.Schema(
         {
-            "days": vol.Coerce(int),
-            "hours": vol.Coerce(int),
-            "minutes": vol.Coerce(int),
-            "seconds": vol.Coerce(int),
-            "milliseconds": vol.Coerce(int),
+            "days": vol.Coerce(float),
+            "hours": vol.Coerce(float),
+            "minutes": vol.Coerce(float),
+            "seconds": vol.Coerce(float),
+            "milliseconds": vol.Coerce(float),
         }
     ),
     has_at_least_one_key("days", "hours", "minutes", "seconds", "milliseconds"),
@@ -357,17 +357,17 @@ def time_period_str(value: str) -> timedelta:
     elif value.startswith("+"):
         value = value[1:]
 
-    try:
-        parsed = [int(x) for x in value.split(":")]
-    except ValueError:
+    parsed = value.split(":")
+    if len(parsed) not in (2, 3):
         raise vol.Invalid(TIME_PERIOD_ERROR.format(value))
-
-    if len(parsed) == 2:
-        hour, minute = parsed
-        second = 0
-    elif len(parsed) == 3:
-        hour, minute, second = parsed
-    else:
+    try:
+        hour = int(parsed[0])
+        minute = int(parsed[1])
+        try:
+            second = float(parsed[2])
+        except IndexError:
+            second = 0
+    except ValueError:
         raise vol.Invalid(TIME_PERIOD_ERROR.format(value))
 
     offset = timedelta(hours=hour, minutes=minute, seconds=second)
@@ -378,10 +378,10 @@ def time_period_str(value: str) -> timedelta:
     return offset
 
 
-def time_period_seconds(value: Union[int, str]) -> timedelta:
+def time_period_seconds(value: Union[float, str]) -> timedelta:
     """Validate and transform seconds to a time offset."""
     try:
-        return timedelta(seconds=int(value))
+        return timedelta(seconds=float(value))
     except (ValueError, TypeError):
         raise vol.Invalid(f"Expected seconds, got {value}")
 
diff --git a/tests/helpers/test_config_validation.py b/tests/helpers/test_config_validation.py
index e6c3757ec55..7da0557c9eb 100644
--- a/tests/helpers/test_config_validation.py
+++ b/tests/helpers/test_config_validation.py
@@ -260,18 +260,49 @@ def test_time_period():
     """Test time_period validation."""
     schema = vol.Schema(cv.time_period)
 
-    options = (None, "", "hello:world", "12:", "12:34:56:78", {}, {"wrong_key": -10})
+    options = (
+        None,
+        "",
+        "hello:world",
+        "12:",
+        "12:34:56:78",
+        {},
+        {"wrong_key": -10},
+        "12.5:30",
+        "12:30.5",
+        "12.5:30:30",
+        "12:30.5:30",
+    )
     for value in options:
         with pytest.raises(vol.MultipleInvalid):
             schema(value)
 
-    options = ("8:20", "23:59", "-8:20", "-23:59:59", "-48:00", {"minutes": 5}, 1, "5")
-    for value in options:
-        schema(value)
-
-    assert timedelta(seconds=180) == schema("180")
-    assert timedelta(hours=23, minutes=59) == schema("23:59")
-    assert -1 * timedelta(hours=1, minutes=15) == schema("-1:15")
+    options = (
+        ("8:20", timedelta(hours=8, minutes=20)),
+        ("23:59", timedelta(hours=23, minutes=59)),
+        ("-8:20", -1 * timedelta(hours=8, minutes=20)),
+        ("-1:15", -1 * timedelta(hours=1, minutes=15)),
+        ("-23:59:59", -1 * timedelta(hours=23, minutes=59, seconds=59)),
+        ("-48:00", -1 * timedelta(days=2)),
+        ({"minutes": 5}, timedelta(minutes=5)),
+        (1, timedelta(seconds=1)),
+        ("5", timedelta(seconds=5)),
+        ("180", timedelta(seconds=180)),
+        ("00:08:20.5", timedelta(minutes=8, seconds=20, milliseconds=500)),
+        ("00:23:59.999", timedelta(minutes=23, seconds=59, milliseconds=999)),
+        ("-00:08:20.5", -1 * timedelta(minutes=8, seconds=20, milliseconds=500)),
+        (
+            "-12:59:59.999",
+            -1 * timedelta(hours=12, minutes=59, seconds=59, milliseconds=999),
+        ),
+        ({"milliseconds": 1.5}, timedelta(milliseconds=1, microseconds=500)),
+        ({"seconds": "1.5"}, timedelta(seconds=1, milliseconds=500)),
+        ({"minutes": "1.5"}, timedelta(minutes=1, seconds=30)),
+        ({"hours": -1.5}, -1 * timedelta(hours=1, minutes=30)),
+        ({"days": "-1.5"}, -1 * timedelta(days=1, hours=12)),
+    )
+    for value, result in options:
+        assert schema(value) == result
 
 
 def test_remove_falsy():