Yes, canned fish is fully cooked during the canning process. The heat used to sterilize and seal the can is intense enough to cook the fish thoroughly, making it safe to eat straight out of the container without any additional heating. This applies to tuna, salmon, sardines, mackerel, and most other canned seafood.
How Canned Fish Gets Cooked
Commercial canning uses a process called retort cooking, which is essentially pressure cooking at extremely high temperatures. Sealed cans are heated to temperatures between 240°F and 280°F, well above the boiling point of water. This destroys all bacteria that could cause spoilage or foodborne illness, including the spores that produce botulism toxin. The result is a product that’s not just cooked but commercially sterile, meaning it can sit on a shelf for years without refrigeration.
The FDA requires that every canned seafood product undergo a thermal process scientifically determined to eliminate microorganisms of public health significance. Manufacturers must have these processes designed by qualified thermal processing experts, and the specific time and temperature combinations vary depending on the type of fish, the can size, and whether the fish is packed in water, oil, or sauce.
Many Fish Are Cooked Twice
Most canned fish actually goes through two rounds of cooking. The first happens before the fish ever enters the can. Large fish like tuna are typically baked at 250°F to 350°F for one to four hours, or steamed until the internal temperature reaches 165°F to 175°F. This pre-cooking firms up the flesh, makes it easier to separate meat from bones and dark tissue, and allows workers to pack the fillets tightly into cans.
Sardines follow a similar pattern but with more variety. Some producers steam sardines on racks before canning. Others fry them in oil, smoke them, or grill them. After this initial preparation, the sardines are packed into cans with oil, water, or sauce, sealed, and then pressure cooked a second time during the retort sterilization step. That second cook is what makes the product shelf-stable.
Smaller operations and some premium brands take a “raw pack” approach for certain fish, placing uncooked fillets directly into cans before the retort step. Even in this case, the retort temperatures are high enough and the processing time long enough that the fish is fully cooked by the end.
The Exception: Canned Anchovies
Anchovies are the notable outlier. Unlike tuna or sardines, most canned anchovies are not heat-cooked at all. Instead, they’re preserved through salt curing, a process where whole anchovies are packed in salt for weeks or months. The heavy salt concentration effectively makes the fish safe to eat without thermal processing, and it gives anchovies their characteristically intense, salty flavor.
Salt-cured anchovies don’t go through pasteurization or retort cooking before canning. They’re technically not “raw” in the way fresh fish is, since the curing process chemically transforms the proteins, but they haven’t been exposed to cooking heat. If you’ve ever wondered why anchovies taste and feel so different from other canned fish, this is the main reason.
Eating Canned Fish Cold
Because the retort process fully cooks and sterilizes the contents, you can safely eat canned tuna, salmon, sardines, and similar products straight from the can at room temperature. No reheating is necessary. This is true whether the fish is packed in water, olive oil, or flavored sauces.
Once you open the can, the sterile seal is broken and bacteria can enter. Any leftover fish should go into a clean container in the refrigerator, where it will keep for three to four days. An unopened can, on the other hand, stays safe for two to five years when stored properly. Retort pouches (the flexible foil packets used for some tuna and salmon) have a shorter recommended shelf life of about 18 months.
One safety note: not all canned seafood is shelf-stable. Certain products, like some canned crab or smoked fish, are labeled “Keep Refrigerated” because they undergo lighter heat treatment. Always check the label before storing canned seafood in the pantry.
What About Can Linings?
Since canned fish is cooked inside the can at high temperatures, some people worry about chemicals leaching from the can’s interior coating into the food. For years, most can linings contained BPA, a compound that raised health concerns. As of 2024, roughly 95% of food cans sold in the U.S. are made with linings that don’t intentionally contain BPA, according to the Can Manufacturers Institute. These newer linings use acrylic, polyester, or polymer-based coatings instead. If avoiding BPA matters to you, many brands now label their cans as BPA-free, and products packed in glass jars or pouches sidestep the question entirely.