diff --git a/homeassistant/core.py b/homeassistant/core.py
index 4c59e88e840..0f2a28b2fa4 100644
--- a/homeassistant/core.py
+++ b/homeassistant/core.py
@@ -1757,7 +1757,9 @@ class StateMachine:
 
         Async friendly.
         """
-        return self._states_data.get(entity_id.lower())
+        return self._states_data.get(entity_id) or self._states_data.get(
+            entity_id.lower()
+        )
 
     def is_state(self, entity_id: str, state: str) -> bool:
         """Test if entity exists and is in specified state.
@@ -1870,10 +1872,16 @@ class StateMachine:
 
         This method must be run in the event loop.
         """
-        entity_id = entity_id.lower()
         new_state = str(new_state)
         attributes = attributes or {}
-        if (old_state := self._states_data.get(entity_id)) is None:
+        old_state = self._states_data.get(entity_id)
+        if old_state is None:
+            # If the state is missing, try to convert the entity_id to lowercase
+            # and try again.
+            entity_id = entity_id.lower()
+            old_state = self._states_data.get(entity_id)
+
+        if old_state is None:
             same_state = False
             same_attr = False
             last_changed = None
diff --git a/tests/test_core.py b/tests/test_core.py
index 4136249f993..efc0b875b4f 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1194,8 +1194,8 @@ async def test_statemachine_remove(hass: HomeAssistant) -> None:
     assert len(events) == 1
 
 
-async def test_statemachine_case_insensitivty(hass: HomeAssistant) -> None:
-    """Test insensitivty."""
+async def test_state_machine_case_insensitivity(hass: HomeAssistant) -> None:
+    """Test setting and getting states entity_id insensitivity."""
     events = async_capture_events(hass, EVENT_STATE_CHANGED)
 
     hass.states.async_set("light.BOWL", "off")
@@ -1204,6 +1204,15 @@ async def test_statemachine_case_insensitivty(hass: HomeAssistant) -> None:
     assert hass.states.is_state("light.bowl", "off")
     assert len(events) == 1
 
+    hass.states.async_set("ligHT.Bowl", "on")
+    assert hass.states.get("light.bowl").state == "on"
+
+    hass.states.async_set("light.BOWL", "off")
+    assert hass.states.get("light.BoWL").state == "off"
+
+    hass.states.async_set("light.bowl", "on")
+    assert hass.states.get("light.bowl").state == "on"
+
 
 async def test_statemachine_last_changed_not_updated_on_same_state(
     hass: HomeAssistant,