How to Tell if Canned Cat Food Is Bad? | Spoilage Signs That Matter

Swollen, leaking, or badly dented cans and food with a foul odor or visible mold are all clear signs canned cat food is bad.

For the full breakdown, see our best Canned Cat Food guide.

Feeding spoiled canned cat food can make your cat sick, yet the warning signs are easy to miss if you aren’t checking before every meal. Your cat can’t tell you the food is off — it relies on you to inspect the can and its contents. This guide covers the exact signs to look for, how to check food safely before serving, and what to do when the answer is in doubt. When you need fresh options, our picks for the best canned cat food offer a solid starting point.

What Does Bad Canned Cat Food Look Like?

Before you even open the can, your eyes and hands are your first tools. A healthy can of cat food should be firm to the touch, with no swelling, leaks, or significant damage to the seal.

Signs that the can itself is compromised include:

• Bulging or swollen ends — pressure inside the can often means gas from bacterial growth.
• Leaks or damp spots — any breach in the seal invites contamination.
• Severe dents, especially along the seams — impact damage can crack the protective lining and let bacteria in.
• Rust or corrosion — this can weaken the metal and compromise the seal over time.

The FDA’s guidance on pet food storage lists a swollen or leaking can or pouch as a clear problem, along with a foul odor, a foreign object, or a pet becoming sick after eating. If the can shows any of these physical defects, discard it without opening it.

How to Inspect the Food Inside the Can

Once you open a can that looks fine, your nose and eyes take over. Trust them — but don’t stop there.

After opening, check for these signs of spoilage:

• Smell: A foul, sour, or rancid odor is an immediate warning sign. Fresh canned cat food has a distinct meaty aroma; anything sour or sharp means trouble.
• Appearance: Visible mold, unusual color changes, or a slimy, gelled texture that isn’t typical for that product are all red flags.
• Texture: Separation can be normal for some foods, but a strange sliminess on the surface is not.

Never taste pet food to check it, and never rely on smell alone. The FDA advises discarding any product you suspect, and some contaminated foods may not smell obviously bad even when they’re unsafe. Inspect the food itself, not just its scent.

Your cat’s behavior can add context, but it’s not proof. A sudden refusal to eat might mean the food has gone off, or it might be a preference or an unrelated health issue. If your cat eats and then becomes sick, the FDA says to throw the remaining food away.

How Long Does Opened Canned Cat Food Last?

Opened canned cat food does not stay fresh indefinitely. Once you break the seal, prompt refrigeration is required, and the safe window varies by manufacturer.

Some manufacturers specify their own guidelines. Other brands may differ, so check the label on your can when it provides guidance.

When in doubt, the AAFCO’s handling guidance is simple: discard food “when in doubt.” It also recommends keeping pet food separate from human food, using clean hands, surfaces, and utensils when serving, and refrigerating unused portions promptly. If you don’t know how long opened food has been sitting in the fridge, don’t risk it.

What Should You Do If the Food Looks Suspicious?

When you spot any sign of spoilage, the answer is straightforward: throw the food out. Don’t try to salvage it by removing the moldy part or reheating it. Bacterial contamination affects the whole can, not just the visible spot.

If your cat has already eaten food you suspect was bad, monitor them closely. The FDA’s guidance says to throw out the product and consult your veterinarian if your pet becomes sick after eating it. Don’t wait for symptoms to worsen before acting — a quick call to your vet is always the safer choice.

The AAFCO’s one-page handling guidance and the FDA’s pet food storage page both make the same core point: when the food looks, smells, or feels wrong, or when the can itself shows damage, the only correct move is to throw it away. The cost of a wasted can is nothing compared to a sick cat.