Can Dogs Have Tuna? What Every Owner Should Know

Dogs can have a small bite of plain, cooked tuna on rare occasions, but tuna is not a safe everyday food. It is high in mercury, and because dogs are small and sensitive to heavy metals, regular tuna can cause a dangerous buildup over time. Many veterinarians recommend safer fish like salmon instead.

That short answer hides a lot of nuance, and honestly, the experts disagree. Below we untangle the conflicting advice, explain exactly why mercury matters, break down canned versus fresh versus raw tuna, and tell you what to do if your dog just polished off a tuna sandwich off the counter.

Is Tuna Safe for Dogs? The Honest Answer

Here is where even trusted sources split. The American Kennel Club takes a firm "no," pointing to tuna's much higher mercury levels compared with fish like salmon and tilapia. Meanwhile, PetMD says dogs can safely eat small amounts of tuna occasionally, as long as it is never a regular part of the diet and never fed to puppies.

So who is right? Both, in a sense. A single small piece of plain tuna is very unlikely to harm a healthy adult dog. The real danger is not one bite; it is tuna becoming a habit. Because the risk is cumulative, the safest and simplest position for most owners is to treat tuna as a food to avoid or to offer only as a tiny, once-in-a-blue-moon treat. If your dog loves fish, there are lower-risk ways to give it to them, which we cover below.

Why Mercury Is the Real Concern

Tuna are large, fast, long-lived predators that eat many smaller fish over their lifetime. Mercury accumulates in their tissue through a process called bioaccumulation, so the biggest tuna species carry some of the highest mercury loads in the ocean. Per the EPA and FDA joint advice on eating fish, tuna—especially bigeye and albacore—sits well above "best choice" low-mercury fish like salmon, sardines, and pollock.

In dogs, mercury is a neurotoxin. Over time, chronic exposure can affect the nervous system and kidneys. Because a 20-pound dog gets a much larger relative dose from the same portion than an adult human would, the margin for error is thinner. This is exactly why the "occasional tiny amount" framing exists: the concern is not acute poisoning from one meal but slow accumulation from tuna showing up in the bowl week after week. There is no established safe daily amount of tuna for dogs, which is why moderation—or avoidance—is the rule.

Canned Tuna vs. Fresh Tuna vs. Raw Tuna

Not all tuna is equal when it comes to dogs:

• Canned tuna in water: The least-bad option if you are going to share. Choose tuna packed in water with no added salt. Skip tuna in oil, which adds unnecessary fat that can upset the stomach or, over time, contribute to pancreatitis risk.
• Canned tuna in oil or brine: Avoid. The extra sodium and fat make an already-questionable food worse.
• Fresh, cooked tuna: Plain, boneless, thoroughly cooked tuna with no salt, garlic, onion, oil, or seasoning is safer than seasoned or canned versions, but it still carries the same mercury concern.
• Raw tuna: Best avoided. Raw fish can harbor parasites and bacteria, and it carries the full mercury load. Cooking does not remove mercury, but it does eliminate those other risks.

Whatever the form, tuna should always be served plain. Common seasonings like onion and garlic are toxic to dogs, and added salt is a problem in its own right.

How Much Tuna Can a Dog Eat?

If you decide to offer tuna at all, keep it firmly in "treat" territory. Veterinary nutrition guidance holds that treats and extras should make up no more than about 10% of a dog's daily calories, with the other 90% coming from a complete, balanced dog food. In practice, that means a small dog might have no more than a teaspoon of plain tuna on a rare occasion, and a large dog perhaps a tablespoon or two—and not on any regular schedule.

Some dogs should skip tuna entirely: puppies, pregnant or nursing dogs, very small breeds, seniors, and any dog with kidney disease or a known health condition. When you are choosing everyday protein for your dog, it belongs in a formulated diet, not in random human foods; our guide to choosing the right protein level in dog kibble is a better roadmap than the tuna can.

Does Tuna Have Any Health Benefits for Dogs?

Tuna is not all downside. Like other fish, it is a lean source of protein and provides omega-3 fatty acids, which support skin and coat health and have anti-inflammatory benefits. PetMD notes that fish is a great natural source of omega-3s that are vital for a healthy coat and skin and can help dogs with conditions like arthritis.

The catch is that you can get every one of those benefits from safer sources without the mercury gamble. Cooked salmon, whitefish, and vet-recommended fish oil supplements deliver the same omega-3s. There is no nutrient in tuna that your dog cannot get somewhere lower-risk, which is a big reason so many vets steer owners elsewhere.

What to Do If Your Dog Ate a Lot of Tuna

First, do not panic. A dog that swiped a tuna sandwich or licked out a can is very unlikely to have an emergency from a single incident. Watch for signs of stomach upset over the next day or two, such as vomiting, diarrhea, or unusual lethargy—more likely from the salt, oil, or seasonings than from mercury itself.

Call your veterinarian right away if your dog ate a very large quantity, if the tuna was heavily salted or seasoned with onion or garlic, or if your dog is small, very young, or has existing health issues. Mercury toxicity from one meal is rare, but symptoms of chronic exposure—like tremors, incoordination, or changes in urination—always warrant a vet visit. When in doubt, a quick phone call to your vet or a pet poison helpline is the right move.

Safer Fish and Treat Alternatives

If your goal is to give your dog fish, reach for the low-mercury options. The AKC specifically recommends cooked salmon and other lower-mercury fish like whitefish, herring, and flounder over tuna. Always serve fish cooked, boneless, and unseasoned. For more fish-treat ideas, see our guide to whether dogs can eat salmon skin. And if your dog has a sensitive stomach, gentle options like a splash of plain chicken broth or purpose-made treats for sensitive stomachs are far more predictable than a tuna experiment.

Frequently Asked Questions

Can dogs eat canned tuna?

In very small amounts on rare occasions, plain canned tuna packed in water with no added salt is generally tolerated by healthy adult dogs. It should never be a regular food, and tuna in oil or brine should be avoided because of the extra fat and sodium.

How much tuna is toxic to a dog?

There is no exact "toxic dose" from a single serving; the concern is mercury building up from repeated feeding. One small bite is very unlikely to cause harm, but tuna eaten regularly can lead to mercury accumulation over time, which is why vets advise keeping it rare or avoiding it.

Can puppies have tuna?

No. Puppies are still developing and are more vulnerable to mercury, so most veterinary sources recommend not giving tuna to puppies at all. Stick to a complete puppy food and vet-approved treats.

Is tuna in water better than tuna in oil for dogs?

Yes. If you share tuna, choose tuna packed in water with no added salt. Tuna in oil adds unnecessary fat that can cause digestive upset, and brine adds sodium your dog does not need.

What fish can dogs eat safely instead of tuna?

Cooked, boneless, unseasoned salmon, whitefish, herring, flounder, and Arctic char are commonly recommended lower-mercury choices. Fish oil supplements are another safe way to provide omega-3 benefits—ask your vet for a product and dose suited to your dog.

The Bottom Line

Tuna sits in a gray area: a tiny, plain, occasional bite is unlikely to hurt a healthy adult dog, but mercury makes it a poor choice for regular feeding and a no-go for puppies and vulnerable dogs. When you want to treat your dog to fish, safer options give you all the benefits with far less risk.

This article is for general information only and is not a substitute for professional veterinary advice. Every dog is different—talk to your veterinarian before adding tuna or any new food to your dog's diet, and contact your vet promptly if your dog shows signs of illness.

Want more clear, vet-informed answers to "can my dog eat this?" questions delivered daily? Subscribe to the Daily Wag newsletter and never second-guess the treat jar again.