Is it possible to restuff a futon mattress that is going soft?

Try a large piece up upholstery foam stuffed on top of the futon inside the cover. Adding more support underneath may help as well.

Yes. You can buy pieces of foam, batting, or Poli-Fil. If your cushion has a zipper filling it will be easy to do.

I think it would be more expensive to use upholstery foam or poli-fil than it would be to buy a new mattress.

Futons are notoriously uncomfortable for sleeping. But, you could use a down comforter as the filling. Don't remove the feathers, just place the whole comforter insider the cushion.

If you’re going to replace I had a very good Serta Futon mattress that WAS actually comfortable to sleep on. Best deals are probably Memorial Day or Labor Day sales. Currently the online retailer with 2 day shipping has them. Lowest price is $139. Good info to know when you price materials to repair as like Judi1 said it may be cheaper to replace. A local mattress store might be able to beat the price I found online as they don’t have to take shipping charges into account when they price their items. Mattress stores are very negotiable and they always run sales. Good luck with either approach

Poli-fil is neither dense enough or thick enough to support weight of bodies sitting or lying down on the futon. It will quickly flatten, shift, and get lumpy.

The filling inside the cover is clearly lopsided and unevenly worn ..

Anything that you try to 'stuff' into the cover,- foam, comforter, etc. as others have suggested, will be also be uneven and lopsided.

You need to remove the old filling completely, then insert either a new futon mattress, or a solid rectangular piece of foam. In my opinion, the latter will be more comfortable. Unfortunately though, solid foam is not inexpensive.

Spread out what is in there , then lay 1 or 2 inexpensive memory foam mattress topper on top under the cover. I would use 2 of the one inch from Walmart. This also makes it nice to sleep on.

Huntress beat me to the answer. Walmart has very inexpensive memory foam mattress toppers. You can open one side of the futon, and place the mattress topper inside and resew the edge. I used this to make a pillow on top of a storage box, worked like a charm.

Three months ago, my wife and I decided to purchase a new mattress. Well, our choice fell on Futon https://bestfutonmattress.net/best-futon-mattresses/. The mattress was ordered over the Internet. Delivery is timely and fast. They delivered the mattress on time. The mattress turned out to be good, there are no traces of punching left as it happens with old cheap mattresses, and it looks very durable. It looks very durable, sleeping on it is very comfortable. My wife and I are satisfied.

Any updates, Patriece? Is there a zipper to open it up? If so, as Zed said you could reach in and shift stuffing around and then beat it with a baseball bat to even it out.

If the mattress has a spring or foam core of some kind (like these hybrids), and the depression is permanent, then buy some cotton or other stuffing to add to that area.

We have a 4" thick Japanese-style futon, and it's pretty easy to move the cotton around in it and beat down the lumps.