Freeze leftover canned tuna only for cooking.

I wouldn’t freeze it for eating straight out of the can.

The problem is water. Canned tuna is already cooked and packed in liquid. Freezing breaks down the fibers further. When you thaw it, the texture turns mushy and watery. Fine for tuna casserole, tuna melts, or mixed into a pasta sauce, but terrible for a tuna salad sandwich.

If you must freeze it, drain it first, then pack it in a freezer-safe container or bag. Squeeze out as much air as you can. Use within three months. Thaw in the fridge overnight, then use it in something that gets cooked or heavily mixed.

Otherwise, just keep the opened can in the fridge in a covered container for three or four days. That’s usually enough time to finish it.

If you’re not going to use it that fast, buy the smaller cans.