diff --git a/homeassistant/components/todoist/calendar.py b/homeassistant/components/todoist/calendar.py
index f89c09451b6..2acd4ea6dc6 100644
--- a/homeassistant/components/todoist/calendar.py
+++ b/homeassistant/components/todoist/calendar.py
@@ -21,7 +21,7 @@ from homeassistant.components.calendar import (
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.const import CONF_ID, CONF_NAME, CONF_TOKEN, EVENT_HOMEASSISTANT_STOP
 from homeassistant.core import Event, HomeAssistant, ServiceCall, callback
-from homeassistant.exceptions import HomeAssistantError, ServiceValidationError
+from homeassistant.exceptions import ServiceValidationError
 from homeassistant.helpers.aiohttp_client import async_get_clientsession
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity_platform import AddEntitiesCallback
@@ -215,14 +215,21 @@ def async_register_services(  # noqa: C901
 
     async def handle_new_task(call: ServiceCall) -> None:  # noqa: C901
         """Call when a user creates a new Todoist Task from Home Assistant."""
-        project_name = call.data[PROJECT_NAME].lower()
+        project_name = call.data[PROJECT_NAME]
         projects = await coordinator.async_get_projects()
         project_id: str | None = None
         for project in projects:
             if project_name == project.name.lower():
                 project_id = project.id
+                break
         if project_id is None:
-            raise HomeAssistantError(f"Invalid project name '{project_name}'")
+            raise ServiceValidationError(
+                translation_domain=DOMAIN,
+                translation_key="project_invalid",
+                translation_placeholders={
+                    "project": project_name,
+                },
+            )
 
         # Optional section within project
         section_id: str | None = None
diff --git a/homeassistant/components/todoist/strings.json b/homeassistant/components/todoist/strings.json
index 55b7ef62b58..5b083ac58bf 100644
--- a/homeassistant/components/todoist/strings.json
+++ b/homeassistant/components/todoist/strings.json
@@ -21,6 +21,9 @@
     }
   },
   "exceptions": {
+    "project_invalid": {
+      "message": "Invalid project name \"{project}\""
+    },
     "section_invalid": {
       "message": "Project \"{project}\" has no section \"{section}\""
     }
diff --git a/tests/components/todoist/test_calendar.py b/tests/components/todoist/test_calendar.py
index 680406096cc..071a14a70ae 100644
--- a/tests/components/todoist/test_calendar.py
+++ b/tests/components/todoist/test_calendar.py
@@ -23,6 +23,7 @@ from homeassistant.components.todoist.const import (
 )
 from homeassistant.const import CONF_TOKEN, Platform
 from homeassistant.core import HomeAssistant
+from homeassistant.exceptions import ServiceValidationError
 from homeassistant.helpers import entity_registry as er
 from homeassistant.helpers.entity_component import async_update_entity
 from homeassistant.util import dt as dt_util
@@ -270,6 +271,25 @@ async def test_create_task_service_call(hass: HomeAssistant, api: AsyncMock) ->
     )
 
 
+async def test_create_task_service_call_raises(
+    hass: HomeAssistant, api: AsyncMock
+) -> None:
+    """Test adding an item to an invalid project raises an error."""
+
+    with pytest.raises(ServiceValidationError, match="project_invalid"):
+        await hass.services.async_call(
+            DOMAIN,
+            SERVICE_NEW_TASK,
+            {
+                ASSIGNEE: "user",
+                CONTENT: "task",
+                LABELS: ["Label1"],
+                PROJECT_NAME: "Missing Project",
+            },
+            blocking=True,
+        )
+
+
 async def test_create_task_service_call_with_section(
     hass: HomeAssistant, api: AsyncMock
 ) -> None: