How to Create Trello Cards from Slack Messages with n8n

api.slack.com > Your Apps > Create New App

Create Slack App and Get Webhook URL

Go to api.slack.com and create a new app for your workspace. You'll need this app to listen for message events and reactions. Set up the Event Subscriptions feature to send data to n8n when specific events happen in your channels.

1. 1Click 'Create New App' and choose 'From scratch'
2. 2Enter app name like 'Trello Card Creator' and select your workspace
3. 3Go to 'Event Subscriptions' in the left sidebar
4. 4Toggle 'Enable Events' to On

n8n > Workflows > + > Webhook

Set Up n8n Webhook Trigger

Create a new workflow in n8n and add a Webhook node as your trigger. This will generate the URL you need for Slack's Event Subscriptions. Configure it to accept POST requests from Slack's event system.

1. 1Click the + button to create a new workflow
2. 2Add a Webhook node from the trigger section
3. 3Set HTTP Method to POST
4. 4Copy the Production URL from the webhook settings

api.slack.com > Your App > Event Subscriptions

Configure Slack Event Subscriptions

Return to your Slack app configuration and paste the n8n webhook URL into the Request URL field. Add the specific events you want to monitor - reaction_added for emoji triggers or message.channels for keyword detection.

1. 1Paste your n8n webhook URL into the Request URL field
2. 2Wait for the green 'Verified' checkmark to appear
3. 3Scroll down to 'Subscribe to bot events'
4. 4Add 'reaction_added' and 'message.channels' events
5. 5Click 'Save Changes' at the bottom

This code snippet adds smart message parsing to extract action items and priority levels from Slack messages before creating Trello cards. Paste it into a Function node between your Slack message retrieval and Trello card creation.

// Extract priority and clean message content
const message = $input.first().json;
const messageText = message.text || '';

// Extract priority and clean message content
const message = $input.first().json;
const messageText = message.text || '';
const user = message.user || 'Unknown';
const channel = $json.event.item.channel;

// Detect priority keywords
let priority = 'normal';
if (messageText.toLowerCase().includes('urgent') || messageText.toLowerCase().includes('asap')) {
  priority = 'high';
} else if (messageText.toLowerCase().includes('nice to have') || messageText.toLowerCase().includes('someday')) {
  priority = 'low';
}

// Extract action items (sentences starting with action words)
const actionWords = ['should', 'need to', 'must', 'have to', 'let\'s', 'we could'];
let actionItem = messageText;
for (const word of actionWords) {
  if (messageText.toLowerCase().includes(word)) {
    const sentences = messageText.split('.');
    const actionSentence = sentences.find(s => s.toLowerCase().includes(word));
    if (actionSentence) {
      actionItem = actionSentence.trim();
      break;
    }
  }
}

// Create enhanced card data
return {
  json: {
    cardName: `[${priority.toUpperCase()}] ${actionItem.substring(0, 50)}`,
    cardDescription: `**Original Message:** ${messageText}\n\n**From:** ${user}\n**Channel:** ${channel}\n**Priority:** ${priority}\n**Created:** ${new Date().toISOString()}`,
    priority: priority,
    labels: priority === 'high' ? ['urgent'] : [],
    dueDate: priority === 'high' ? new Date(Date.now() + 7 * 24 * 60 * 60 * 1000).toISOString() : null
  }
};

api.slack.com > Your App > OAuth & Permissions

Add OAuth Scopes and Install App

Your Slack app needs specific permissions to read messages and reactions. Add the required OAuth scopes, then install the app to your workspace to generate the bot token you'll use in n8n.

1. 1Go to 'OAuth & Permissions' in the left sidebar
2. 2Scroll to 'Scopes' and add 'channels:history' and 'reactions:read'
3. 3Click 'Install to Workspace' at the top
4. 4Authorize the app in the popup window
5. 5Copy the 'Bot User OAuth Token' that starts with xoxb-

n8n > Credentials > + > Trello API

Set Up Trello Authentication

Create credentials for Trello in n8n by getting your API key and token from Trello's developer portal. You'll need these to create cards and access your boards programmatically.

1. 1Go to trello.com/app-key to get your API key
2. 2Click the Token link to generate an access token
3. 3Return to n8n and click 'Create New Credential'
4. 4Select 'Trello API' and paste your key and token
5. 5Test the connection and save

Workflow > + > Logic > IF

Add Message Filtering Logic

Add an IF node after your webhook to filter incoming Slack events. You want to process only reaction_added events with specific emojis or message events containing trigger keywords. This prevents your workflow from firing on every Slack message.

1. 1Add an IF node after your webhook trigger
2. 2Set condition 1: event.type equals 'reaction_added'
3. 3Add condition 2: event.reaction equals 'memo' (for 📝 emoji)
4. 4Set the logic to OR between conditions
5. 5Connect the True output to continue the workflow

Workflow > + > Regular Nodes > Slack

Get Original Message Content

When someone reacts to a message, Slack only sends the reaction event - not the original message text. Add a Slack node to fetch the full message content using the channel and timestamp from the reaction event.

1. 1Add a Slack node after your IF condition
2. 2Choose 'Get Message' operation
3. 3Set Channel to {{$json.event.item.channel}}
4. 4Set Timestamp to {{$json.event.item.ts}}
5. 5Use your Slack bot credentials

Workflow > + > Regular Nodes > Trello

Configure Trello Card Creation

Add a Trello node to create new cards with the message content. Map the Slack message text to the card description, use the original message author for context, and set the appropriate board and list where cards should appear.

1. 1Add a Trello node after your Slack message node
2. 2Choose 'Create a Card' operation
3. 3Select your target board from the dropdown
4. 4Choose the list where new cards should appear
5. 5Set card name to a combination of channel and user info

Trello Node > Parameters

Map Slack Data to Card Fields

Configure the card fields to pull relevant information from the Slack message. Set up the card name, description, and any labels or due dates based on the message content and context from your Slack channel.

1. 1Set Card Name to 'Action: {{$node["Slack"].json["text"].substring(0, 50)}}'
2. 2Set Description to include full message text and channel context
3. 3Add the message author using {{$node["Slack"].json["user"]}}
4. 4Include channel name with {{$json.event.item.channel}}
5. 5Set any default labels for Slack-created cards

Workflow > Save > Activate

Test and Activate Workflow

Save your workflow and activate it, then test the integration by going to Slack and reacting to a message with the 📝 emoji. Check that the card appears in your designated Trello board with the correct information.

1. 1Click Save in the top right of your workflow
2. 2Toggle the Active switch to enable the workflow
3. 3Go to a Slack channel where your bot is invited
4. 4React to any message with the 📝 emoji
5. 5Check your Trello board for the new card