diff --git a/homeassistant/components/todoist/calendar.py b/homeassistant/components/todoist/calendar.py
index f81a4a7249a..978e58c2500 100644
--- a/homeassistant/components/todoist/calendar.py
+++ b/homeassistant/components/todoist/calendar.py
@@ -39,6 +39,9 @@ from .const import (
     PROJECT_ID,
     PROJECT_NAME,
     PROJECTS,
+    REMINDER_DATE,
+    REMINDER_DATE_LANG,
+    REMINDER_DATE_STRING,
     SERVICE_NEW_TASK,
     START,
     SUMMARY,
@@ -56,6 +59,11 @@ NEW_TASK_SERVICE_SCHEMA = vol.Schema(
         vol.Exclusive(DUE_DATE_STRING, "due_date"): cv.string,
         vol.Optional(DUE_DATE_LANG): vol.All(cv.string, vol.In(DUE_DATE_VALID_LANGS)),
         vol.Exclusive(DUE_DATE, "due_date"): cv.string,
+        vol.Exclusive(REMINDER_DATE_STRING, "reminder_date"): cv.string,
+        vol.Optional(REMINDER_DATE_LANG): vol.All(
+            cv.string, vol.In(DUE_DATE_VALID_LANGS)
+        ),
+        vol.Exclusive(REMINDER_DATE, "reminder_date"): cv.string,
     }
 )
 
@@ -181,13 +189,34 @@ def setup_platform(hass, config, add_entities, discovery_info=None):
                 due_date = datetime(due.year, due.month, due.day)
             # Format it in the manner Todoist expects
             due_date = dt.as_utc(due_date)
-            date_format = "%Y-%m-%dT%H:%M"
+            date_format = "%Y-%m-%dT%H:%M%S"
             due_date = datetime.strftime(due_date, date_format)
             _due["date"] = due_date
 
         if _due:
             item.update(due=_due)
 
+        _reminder_due: dict = {}
+        if REMINDER_DATE_STRING in call.data:
+            _reminder_due["string"] = call.data[REMINDER_DATE_STRING]
+
+        if REMINDER_DATE_LANG in call.data:
+            _reminder_due["lang"] = call.data[REMINDER_DATE_LANG]
+
+        if REMINDER_DATE in call.data:
+            due_date = dt.parse_datetime(call.data[REMINDER_DATE])
+            if due_date is None:
+                due = dt.parse_date(call.data[REMINDER_DATE])
+                due_date = datetime(due.year, due.month, due.day)
+            # Format it in the manner Todoist expects
+            due_date = dt.as_utc(due_date)
+            date_format = "%Y-%m-%dT%H:%M:%S"
+            due_date = datetime.strftime(due_date, date_format)
+            _reminder_due["date"] = due_date
+
+        if _reminder_due:
+            api.reminders.add(item["id"], due=_reminder_due)
+
         # Commit changes
         api.commit()
         _LOGGER.debug("Created Todoist task: %s", call.data[CONTENT])
diff --git a/homeassistant/components/todoist/const.py b/homeassistant/components/todoist/const.py
index a1e37bf0292..c83567981af 100644
--- a/homeassistant/components/todoist/const.py
+++ b/homeassistant/components/todoist/const.py
@@ -24,6 +24,10 @@ DUE = "due"
 DUE_DATE_STRING = "due_date_string"
 # Service Call: The language of DUE_DATE_STRING
 DUE_DATE_LANG = "due_date_lang"
+# Service Call: When should user be reminded of this task (in natural language)?
+REMINDER_DATE_STRING = "reminder_date_string"
+# Service Call: The language of REMINDER_DATE_STRING
+REMINDER_DATE_LANG = "reminder_date_lang"
 # Service Call: The available options of DUE_DATE_LANG
 DUE_DATE_VALID_LANGS = [
     "en",
@@ -44,6 +48,8 @@ DUE_DATE_VALID_LANGS = [
 # Attribute: When is this task due?
 # Service Call: When is this task due?
 DUE_DATE = "due_date"
+# Service Call: When should user be reminded of this task?
+REMINDER_DATE = "reminder_date"
 # Attribute: Is this task due today?
 DUE_TODAY = "due_today"
 # Calendar Platform: When a calendar event ends
diff --git a/homeassistant/components/todoist/services.yaml b/homeassistant/components/todoist/services.yaml
index 186b15a18a9..88c057c1ef8 100644
--- a/homeassistant/components/todoist/services.yaml
+++ b/homeassistant/components/todoist/services.yaml
@@ -20,5 +20,14 @@ new_task:
       description: The language of due_date_string.
       example: en
     due_date:
-      description: The day this task is due, in format YYYY-MM-DD.
+      description: The time this task is due, in format YYYY-MM-DD or YYYY-MM-DDTHH:MM:SS, in UTC timezone.
       example: "2019-10-22"
+    reminder_date_string:
+      description: When should user be reminded of this task, in natural language.
+      example: Tomorrow
+    reminder_date_lang:
+      description: The language of reminder_date_string.
+      example: en
+    reminder_date:
+      description: When should user be reminded of this task, in format YYYY-MM-DDTHH:MM:SS, in UTC timezone.
+      example: "2019-10-22T10:30:00"