Sarah Yeung posted in the Asana forum on 24 October 2025. The content team had one Trello board that spanned several years. They wanted it in Asana for history, not as a live sync.
CSV and the extensions they tried were too small, or they dropped the fields that made the board useful. The thread closes a month later with no clean import. That is the story. A multi-year board is not a spreadsheet.
If you are looking at the same route, start with the Trello → Asana playbook. Asana will import from other tools. Trello will export a board. Comments are the part both sides treat as optional.
What the native path drops
Trello’s CSV is cards, lists, labels, and a few dates. Activity, comments, attachments, and Power-Ups stay in Trello or in a JSON export you still have to map. Asana’s CSV importer turns rows into tasks. It does not rebuild a comment thread.
Sarah listed the tools that already failed. Migrator-xyz. Trello’s own CSV. The Trelloexport Chrome extension. An “export Trello to Excel” extension. The missing pieces were the same each time: comments, attachments, and subtasks. When something did land, it often dumped into the Asana task description as unstructured text.
That dump might be enough if you only need a graveyard. Sarah said formatting would be nice. It was not the requirement. History was.
Paid importers were not a full answer either
David Jane pointed at Altosio. Bryan from TeamKickstart mentioned Unito, which he had used on large Trello boards seven or eight years earlier. He also said Unito now sells a separate migration package he has not priced. Larry Berger said he had used Altosio on a couple of Trello moves and liked the support.
Sarah’s team tried both.
Unito would only sync going forward. It would not import the existing board. Duplicating the Trello board as a workaround still left them copying by hand.
Altosio moved content, with limits they wrote down. Media files did not always transfer. Subtasks arrived without notes or attachments. Text formatting broke in the Asana description. They asked if other Altosio users had seen the same gaps. Larry sent them to Altosio support. Andrés at Connex said a custom API job can keep comments, attachments, and subtasks, at a higher price, because the Trello API is complete and fragmented.
The thread was closed on 27 November 2025. There is no “we finished” reply. I am not inventing a successful cutover.
What I would copy
Test comments, attachments, and checklists on the largest board first. Sarah’s years of cards were the thing that broke the free exporters. A five-card sample will lie.
Decide whether history is a requirement. If comments are the reason you are moving, Asana CSV is the wrong tool. Budget an importer or an API job, and read that vendor’s loss list before you pay per project.
If someone offers a sync tool, ask whether it copies the old cards or only new ones. Unito did not import Sarah’s existing data.
Keep the Trello board readable until you can open a known card in Asana and see the same comments and files. This team never posted that check.
The Trello → Asana playbook is the checklist. Use Sarah’s thread for the comment gap a green CSV import will not mention.