Fresh, uncooked tuna keeps in the refrigerator for up to two days before it should be used or frozen. A prepared dish like tuna salad is safe for up to five days, while cooked tuna leftovers should be eaten within four days for maximum safety.
To maximize the amount of time tuna remains fresh, keep it in the coldest part of the refrigerator. Store it on the bottom shelf, as far away from the door as possible. If tuna is to be kept beyond a few days in the refrigerator, it should be moved to the freezer for long-term storage.