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Can Slack attachments get sent to a Trello card

Kjrsti Hoole
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August 4, 2026

Greetings, 

I have set up a Zapier form that gets uploaded, creates a card in Trello but if someone attaches something, it wont port into Trello. 

I found that the way Zapier stores file is not compatible with Trello so now I have the attachments linked to a Trello board URL that shows up in slack so we can click and drag the attachment to the correct card. 

Is there a way to automate it so when and attachment comes through, connected to a dedicated card the attachment can upload to the Trello card without having to click and drag?

Here is how is comes through in Slack: 
image.png

Thank you in advance for any suggestions! 

1 answer

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Arkadiusz Wroblewski
Community Champion
August 4, 2026

Hallo @Kjrsti Hoole 

If you can share which form app you are using and what attachment-related fields Zapier gives you in the trigger output (with any private URLs removed), we can probably work out exactly which field should go into Add Attachment to Card.

Btw. That you are on track, you are not first one asking about that.

https://community.atlassian.com/forums/Trello-questions/Attachment-from-slack/qaq-p/2188623 

https://community.atlassian.com/forums/Trello-questions/can-I-attach-a-file-for-example-image-directly-from-slack-to/qaq-p/595039 

Best,

Arek 🤠 

Kjrsti Hoole
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August 5, 2026

Hey @Arkadiusz Wroblewski 

Thanks for getting back to me!

I am using the Zapier Form with their attachment option in the form. 

In the "add attachment to card" action I have used both the URL and File attachment. 
I have found that when I use the File attachment, it stops the card from coming through and when I use the URL it just sends the metadata. 

I was trying the chat box in Zapier and we ran about 30 different runs doing it different ways, but it seems Trello wont bring it in. I was able to send the attachment to Slack so not it sends over a link to the Trello card so we can do a drag and drop. But they really just want that automated as well. 

Arkadiusz Wroblewski
Community Champion
August 5, 2026

Test with a single file, map the file object directly to File Attachments, leaving URL Attachments empty.

Check Zap History for the attachment step error; note multiple files need Looping by Zapier.

Kjrsti Hoole
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August 6, 2026

Myself and my team have been unsuccessful. We have tried looping in the best we got and still can't manage. From what we are seeing, it is an issue with Trllo allowing the data to import in. 

We have just decided to have Zapier send attachments to slack with a URL to the dedicated Trello card and drag and dop it. That has been the only thing to work for us. 

Thank you for trying to help Arek! I really do appreciate it. 

Arkadiusz Wroblewski
Community Champion
August 7, 2026

Zapier distinguishes between real file objects and URLs, Slack file URLs fail in Trello because they require authentication. That's mainly problem.

Try a two-Zap workaround:

 Pass the generated Trello Card ID into your Slack step in Zap 1.

 Trigger Zap 2 on Slack –> New File, mapping Slack's actual file object into Trello –> Add Attachment to Card using that Card ID.

Zapier offers a pre-built template for this exact Slack-to-Trello file handoff.

https://help.zapier.com/hc/en-us/articles/32816445802893-Use-the-file-upload-field-type-in-Zapier-Forms 

If that won't work, then well I recommend contact with https://zapier.com/app/get-help 

Cheers 

Arek 🤠 

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