How to Assign Todoist Tasks from Slack Mentions with Power Automate

make.powerautomate.com > My flows > + New flow > Automated cloud flow

Create a new Automated cloud flow in Power Automate

Go to make.powerautomate.com and sign in. In the left sidebar click 'My flows', then click '+ New flow' in the top menu. Select 'Automated cloud flow' from the dropdown — this is the correct type because the trigger is an external event, not a schedule. Give your flow a name like 'Slack Mention → Todoist Task' and click 'Create'.

1. 1Click 'My flows' in the left sidebar
2. 2Click '+ New flow' at the top of the page
3. 3Select 'Automated cloud flow'
4. 4Enter a flow name: 'Slack Mention → Todoist Task'
5. 5Click 'Skip' on the trigger picker — you will set it in the next step

Flow canvas > Trigger block > Search: Slack > When a new message is posted to a channel

Add the Slack trigger: 'When a new message is posted to a channel'

Click the empty trigger block on the canvas. In the search bar type 'Slack' and select the Slack connector. Choose the trigger 'When a new message is posted to a channel'. This trigger uses a webhook registered by Power Automate directly with Slack's API — no polling interval to configure. You will be prompted to authenticate your Slack workspace if you have not connected it before.

1. 1Click the trigger block labeled 'When this happens...'
2. 2Type 'Slack' in the connector search bar
3. 3Click the Slack connector card
4. 4Select 'When a new message is posted to a channel' from the trigger list
5. 5Click 'Sign in' and authenticate with your Slack workspace credentials

Flow canvas > Slack trigger > Channel Name dropdown

Select the target Slack channel

In the trigger configuration, click the 'Channel Name' dropdown. Power Automate will load the list of public channels your authenticated Slack user can see. Select the specific project channel you want to monitor, such as #client-acme. If you want to monitor multiple channels, you will need to either duplicate this flow per channel or use a filter in a later step after selecting a broad channel.

1. 1Click the 'Channel Name' dropdown inside the trigger block
2. 2Wait for the channel list to load (takes 3-5 seconds)
3. 3Select your target channel, e.g., 'client-acme'
4. 4Leave all other trigger fields at their defaults

Flow canvas > + New step > Control > Condition

Add a Condition to filter only messages containing an @mention

Not every message in the channel should create a task — only messages where a team member is mentioned. Click '+ New step', search for 'Condition', and select the 'Condition' control. In the left value field, insert the dynamic value 'Text' from the Slack trigger (this is the raw message text). Set the operator to 'contains'. In the right value field, type '<@' — this is how Slack encodes user mentions in its API payload (e.g., '<@U04XKBT2J>'). Only messages with at least one mention will pass through to the Yes branch.

1. 1Click '+ New step' below the trigger
2. 2Search for 'Condition' and select it from Control
3. 3Click into the left value field and select dynamic value 'Text' from the Slack trigger
4. 4Set the operator dropdown to 'contains'
5. 5Type '<@' in the right value field

Flow canvas > Yes branch > Add an action > Data Operation > Compose

Parse the mentioned user ID from the message text

Inside the 'Yes' branch, click 'Add an action'. Search for 'Compose' and add a Data Operation > Compose action. You will use a Power Automate expression to extract the user ID from the raw Slack mention string. In the Inputs field, click 'Expression' tab and enter the formula shown in the pro tip section. This extracts the string between '<@' and '>' to get the raw Slack user ID (e.g., U04XKBT2J). You will map this to the Todoist assignee in a later step.

1. 1Click 'Add an action' inside the Yes branch
2. 2Search for 'Compose' and select 'Data Operation > Compose'
3. 3Click into the Inputs field
4. 4Switch to the 'Expression' tab in the dynamic content panel
5. 5Enter the extraction expression (see pro tip) and click OK

Flow canvas > Yes branch > Add an action > Slack > Get user profile

Look up the Slack user's display name

The Compose step outputs a Slack user ID like U04XKBT2J, which is not human-readable. Add a new action: search for 'Slack' and choose 'Get user profile'. Pass in the output of the Compose step (Outputs from the previous action) as the User ID field. This API call returns the user's display name, real name, and email. You will use the display name as the assignee label on the Todoist task.

1. 1Click 'Add an action' below the Compose step
2. 2Search for 'Slack' in the connector search
3. 3Select 'Get user profile'
4. 4In the User ID field, insert the dynamic value 'Outputs' from the previous Compose step

Flow canvas > Yes branch > Add an action > Todoist > Sign in

Connect your Todoist account

Add a new action and search for 'Todoist'. Select 'Todoist' from the connector list. Power Automate will immediately prompt you to sign in — click 'Sign in' and authenticate with the Todoist account that owns the project you want tasks created in. This creates a Connection entry in your Power Automate Connections list. The connection is tied to a single Todoist account, so tasks will appear in that account's projects.

1. 1Click 'Add an action' below the Slack user profile step
2. 2Search for 'Todoist' in the connector search bar
3. 3Select any Todoist action temporarily to trigger authentication
4. 4Click 'Sign in' in the connection prompt
5. 5Authenticate with your Todoist credentials in the popup window

Flow canvas > Yes branch > Todoist > Create task

Add the Todoist 'Create task' action and map fields

With Todoist connected, change the action to 'Create task'. The action form shows fields for Content, Project ID, Due Date, Priority, and Labels. Map the fields as follows: set Content to a combination of the Slack message Text dynamic value; set Project ID by clicking the dropdown and selecting your target project; set Labels to the Slack Channel Name dynamic value from the trigger so each task is tagged with its source channel. Leave Due Date blank unless your team uses a standard SLA.

1. 1Change or set the Todoist action to 'Create task'
2. 2Click the Content field and insert dynamic value 'Text' from the Slack trigger
3. 3Click the Project ID dropdown and select your target Todoist project
4. 4Click the Labels field and insert dynamic value 'Channel Name' from the Slack trigger
5. 5Optionally set Priority to 2 (high) for mention-based tasks

Flow canvas > Yes branch > Todoist > Create task > Description field

Add a task description with channel and sender context

The Todoist 'Create task' action has a Description field (sometimes labeled 'Note'). Click it and build a context string using dynamic values: insert 'Channel Name' from the Slack trigger, then the Slack message 'Text', then 'Message Timestamp' formatted as a readable date. This gives the assignee full context without needing to open Slack. The description should read something like: 'From #client-acme on [timestamp]: [full message text]'.

1. 1Click the Description field inside the Create task action
2. 2Type 'From #' then insert the dynamic value 'Channel Name'
3. 3Type ' on ' then insert dynamic value 'Message Timestamp'
4. 4Press Enter and insert dynamic value 'Text' from the Slack trigger

This expression goes in the Inputs field of the Compose action (Step 5). It extracts the Slack user ID from the raw mention string format '<@USERID>'. Paste it in the Expression tab of the dynamic content panel — do not type it in the regular field editor or the syntax will break.

// Power Automate Expression — paste into the Compose action's Inputs field
// Extracts Slack user ID from mention format: <@U04XKBT2J>
substring(

// Power Automate Expression — paste into the Compose action's Inputs field
// Extracts Slack user ID from mention format: <@U04XKBT2J>

substring(
  triggerBody()?['text'],
  add(indexOf(triggerBody()?['text'], '<@'), 2),
  sub(
    indexOf(triggerBody()?['text'], '>'),
    add(indexOf(triggerBody()?['text'], '<@'), 2)
  )
)

// Result: 'U04XKBT2J'
// Use 'Outputs' from this Compose step as the User ID input in Get user profile

// Bonus: readable timestamp expression for the task description field
// Paste this separately in the Description field expression editor:
formatDateTime(
  addSeconds('1970-01-01T00:00:00Z', int(first(split(triggerBody()?['ts'], '.')))),
  'yyyy-MM-dd HH:mm'
)
// Result: '2024-04-12 14:00'

Flow canvas > Yes branch > Add an action > Slack > Post message

Post a confirmation message back to Slack

Add one final action inside the Yes branch: search for Slack and select 'Post message'. Set the Channel to the same channel from the trigger. In the Message Text field, type 'Task created for ' and then insert the 'Real Name' dynamic value from the 'Get user profile' step. This closes the loop so the team knows the task was captured without checking Todoist manually.

1. 1Click 'Add an action' below the Todoist Create task step
2. 2Search for 'Slack' and select 'Post message'
3. 3Set Channel to the same channel from the trigger using the dynamic value 'Channel Name'
4. 4In Message Text type 'Task created for ' and insert dynamic value 'Real Name' from Get user profile
5. 5Click Save

Flow canvas > Save > Test > Manually

Test the flow end-to-end and turn it on

Click 'Save' in the top menu, then click 'Test' and select 'Manually'. Go to the target Slack channel and post a message that includes a @mention, such as '@jordan please review the landing page copy'. Return to Power Automate — the test panel will show each step either green (success) or red (failure) with the actual data passed. Verify the Todoist task appeared in the correct project and the Slack confirmation message posted. Once confirmed, the flow is already live — no additional activation step is needed after a successful test save.

1. 1Click 'Save' in the top toolbar
2. 2Click 'Test' then select 'Manually'
3. 3Go to your Slack channel and post a message with a @mention
4. 4Return to Power Automate and watch the test run panel
5. 5Check Todoist to confirm the task was created in the correct project