A cloud-based identity and access management service for securing user authentication and resource access
Hello Samuel JN,
I understand you're trying to download attachments from a SharePoint list item using Microsoft Graph.
You're correctly using this endpoint to check whether attachments exist or not:
GET https://graph.microsoft.com/v1.0/sites/{site-id}/lists/{list-id}/items/{item-id}?expand=fields(select=Title,Attachments)

This API confirms if attachments are present (true or false), but it doesn’t return the actual files.
Currently, Microsoft Graph does not support downloading attachments from SharePoint list items. As a workaround, you can use the SharePoint REST API, which does support this functionality.
To list all attachments for a list item, use:
GET https://{tenant}.sharepoint.com/sites/{site-name}/_api/web/lists/getbytitle('{list-title}')/items({item-id})/AttachmentFiles

To download a specific file, like logo.jpg, use below SharePoint REST API call:
GET https://{tenant}.sharepoint.com/sites/{site-name}/_api/web/lists/getbytitle('{list-title}')/items({item-id})/AttachmentFiles('logo.jpg')/$value

If you're using Postman, the file might be saved as response.bin. You can simply rename it to the original file name (such as logo.jpg), and it will open correctly.
You can find a related suggestion already posted on the Microsoft Feedback Portal:
https://feedbackportal.microsoft.com/feedback/idea/5272d0ff-74b2-ef11-95f5-6045bdbc7c39
Feel free to upvote it to help raise visibility. Many Microsoft Graph features are prioritized based on customer feedback, and with more demand, support for downloading list item attachments may be considered in future updates.
You can also check this related Microsoft Q&A thread confirming the limitation and workaround:
Hope this helps!
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If you have any other questions or are still experiencing issues, feel free to ask in the "comments" section, and I'd be happy to help.