While Asana continues to work on this feature (or ignore us completely) here’s a hack that might come in handy -
The auto-hiding of completed subtasks does not work in the List view but it does work in the Board view. You can toggle between seeing all tasks and incomplete tasks - the filter also gets applied to subtasks automatically.
This makes me think this is a bug in the list view that has needed fixing for approx. 3 yrs now.
Thanks for the tip! I was excited to try it, but the reverse happened for me: showing only incomplete tasks hid the completed subtasks in the list view but not in the board view. 
I wish it worked for me that way. I was more interested in the list view than the Board view but this seems only work for me in the Board view. However, slowly I’m getting used to the Board view, it’s not that bad.
I too would like to ask that Asana sorts this out. I have subtasks inside or subtasks and the board view does not allow me to fix this as suggested above so it is not ideal and puts people off using it effectively.
Hello, is there an update on this? It has been 2 years and this seems like a pretty straightforward feature request…
This is a needed feature in subtasks, it’s already in the main view option why not subtask? Please @asana
Since Asana will get around to this around the same time you get your $10 back from your friend in high school, in the meantime, I have found it helps keep tasks clean if you just delete the completed subtasks. You can still access them in the deleted items section. Not a perfect solution as it would be nice to have these nested under its parent task but at least you won’t see a ton of completed subtasks.
Omg this hasn’t been added yet?? 
any updates on this @Marie ?
Oh my God. It’s been 4 years if not more. What is wrong with you, Asana? Fix this glaringly obvious usability flaw already!
I’m adding to this as well! It’s driving me mad!
This seems like basic list/todo functionality. I can’t believe it’s taken this long to do this.
Also, what does the “save default view” feature do if it does not “save a view as default”.
YES PLEASE!!! This is such a basic feature. Please include that ASAP!
When I complete a subtask it is marked as “complete” but the subtask remains in the list. It should vanish into “completed subtasks” in the same manner as completed tasks. I should later be able to view completed subtasks (completed, incomplete, all, etc.).
Wow, nearly 4 years, 433 votes, aaaaand… nothing happened, anyone from Asana, any update on this? maybe for the 4th anniversary of the first request, could you please surprise us?
I agree! This would be super helpful. +1
+1 here as well. We switched to Asana from Todoist and now I wish we stayed on Todoist because recurring tasks are so messy in Asana. At least we can filter main tasks to show only incomplete tasks but the subtasks are a nightmare. I love Asana otherwise, Please please please fix!
@Emily_Roman @Rebecca_McGrath any updates on this one?
Agree with the above comments. It is causing colleagues to avoid using Asana and turn to other applications to Manage project in apps like Notion given how cluttered this makes Asana.
It would be great if this could be an option set at organisation level so we don’t have to keep adjusting the filter view.
Given Asana prides itself on reducing repetitive work and helpful people and organisations focus on important work this should be a priority fix rather than adding in new features in my opinion.
I’ve recently started using Asana again and this really leaps out as a required feature. Can anyone shed light on why it’s been 4 years and no movement whatsoever? Even if it’s flagged as low priority, 4 years?! This feels like a feature you’d assign to a new starter to get it moving
Everything else seems really polished. Thanks for an otherwise great solution
+1 pretty pretty pretty pretty please add this feature.
It can’t be that hard considering it works with tasks? Why not subtasks?
C’moonnnnnnnnnnnn please