Can dogs eat tuna?
Safe in moderationDogs can eat small amounts of plain tuna occasionally, but mercury and sodium mean it shouldn't be a regular food.
Reviewed by the Webvet Veterinarian Team · Last reviewed June 26, 2026
Can Dogs Eat Tuna?
Dogs can eat small amounts of plain tuna occasionally, but mercury and sodium mean it should never be a regular part of their diet. A spoonful of plain tuna canned in water, drained and unsalted, is not toxic and is unlikely to hurt a healthy dog. The problem is not a single serving. It is what happens when tuna becomes a routine, because the mercury it carries builds up in the body over time and the salt in most canned products adds up fast in a much smaller animal than a human.
- 1Plain tuna is not toxic to dogs, but it is an occasional treat, not a staple food.
- 2Mercury accumulates with frequent feeding, which is the single biggest reason to keep tuna rare.
- 3Always choose tuna canned in water with no added salt, and drain it well before serving.
- 4Skip tuna packed in oil or brine, and never feed tuna mixed with mayonnaise, onion, or garlic.
- 5Salmon and sardines are lower-mercury fish that make better regular choices.
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Is tuna safe for dogs?
Yes, in the sense that plain cooked tuna or tuna canned in water is non-toxic and will not poison your dog the way grapes, onions, or chocolate can. Tuna is high in protein and rich in omega-3 fatty acids, and it also supplies vitamin B12 and selenium. Those are genuinely useful nutrients, which is why fish shows up in so many commercial dog foods. The catch is that your dog is almost certainly already getting balanced fish-based nutrition from a complete diet, so plain tuna adds very little that a well-fed dog actually needs.
Grain-free beef and bison bites for a meaty reward that stays inside the treat budget.
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The word to hold onto is moderation. Tuna is safe as a rare treat and risky as a habit. A small spoonful shared once in a while is fine for most healthy adult dogs. A daily scoop, or tuna used to make a picky dog finish a meal, is where the trouble starts. The difference between a harmless treat and a slow problem is almost entirely about frequency and portion size, not about tuna being poisonous.
Why mercury is the real concern
Tuna are large, long-lived predatory fish, and they sit near the top of the ocean food chain. Every smaller fish they eat carries a trace of mercury, and that mercury concentrates in the tuna's body over its lifetime through a process called bioaccumulation. This is why tuna consistently tests higher for mercury than smaller fish like sardines. When your dog eats tuna, that mercury does not simply pass through. It can build up in their tissues, and over months of frequent feeding it can reach levels that affect the nervous system and kidneys.
This is the core reason vets treat tuna as an occasional food rather than a regular one. A single small serving delivers a tiny amount of mercury that a healthy dog clears without issue. The danger is cumulative. Feed tuna a few times a week, every week, and the exposure stacks up faster than the body can clear it. Smaller dogs reach a concerning dose sooner than large dogs simply because the same spoonful is a bigger share of their body weight. Signs of mercury poisoning are rare but serious, and can include loss of coordination, tremors, hair loss, and changes in urination.
Canned in water vs oil vs brine
If you are going to share tuna, the packing liquid matters as much as the fish. Tuna canned in fresh water with no added salt is the only version worth offering a dog, and even then you should drain it well before serving. Water-packed tuna keeps the extras to a minimum, so what your dog gets is mostly the fish itself.
Tuna packed in oil is a poor choice. The added fat is unnecessary calories that can upset a dog's stomach and, in richer amounts or in dogs prone to it, contribute to pancreatitis. Tuna in sunflower oil, olive oil, or any oil should be skipped. Tuna in brine or salt water is worse in a different way, because the salt content is high and dogs are far more sensitive to sodium than we are. Salted, seasoned, or flavored tuna pouches often add garlic and onion powder too, both of which are toxic to dogs. If the only tuna in the house is packed in oil or brine, it is better to skip the treat than to serve it.
| Tuna type | Safe for dogs? | Why |
|---|---|---|
| Canned in water, no salt | Best option, occasionally | Just fish and water, easy to drain |
| Canned in oil | Avoid | Extra fat, stomach upset, pancreatitis risk |
| Canned in brine or salt water | Avoid | Too much sodium for a dog |
| Flavored or seasoned pouches | Never | Often contain toxic onion and garlic |
| Raw tuna | Avoid | Parasite risk and higher mercury exposure |
How much tuna can a dog have?
The honest answer is not much and not often. A safe serving is a small spoonful of plain tuna in water, offered once in a while rather than on a schedule. Like any treat, tuna should stay within the ten percent rule, meaning treats and extras together should make up no more than ten percent of your dog's daily calories, with the remaining ninety percent coming from a complete and balanced dog food. Because tuna also carries mercury, most vets suggest keeping it well below what that calorie math alone would allow.
Size is the biggest variable. A tiny amount that is harmless for a large-breed dog is a much bigger dose for a small dog, both in calories and in mercury. The table below gives rough starting points for an occasional treat, not a daily allowance. When in doubt, feed less, and always check with your own vet if your dog has kidney issues, is pregnant, or is on a restricted diet.
| Dog size | Occasional tuna serving | How often |
|---|---|---|
| Small (under 20 lb) | 1 teaspoon, drained | Rarely, a couple of times a month at most |
| Medium (20 to 50 lb) | 1 to 2 teaspoons, drained | Occasionally, not weekly |
| Large (over 50 lb) | 1 tablespoon, drained | Occasionally, not weekly |
How to prepare and serve tuna safely
Preparing tuna for a dog is mostly about taking things away rather than adding them. Start with plain tuna canned in water, or plain tuna you have cooked yourself with no oil, butter, or seasoning. Drain it thoroughly to shed as much of the liquid and salt as possible. Serve it on its own, or mix a small flake into your dog's regular food as an occasional topper. Keep the portion to the amounts above and watch how your dog handles it the first time.
A better fish for a dog than canned tuna: wild salmon, freeze-dried, one ingredient, and none of the mercury or brine concerns.
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Just as important is what to leave out. Do not add salt, oil, or butter. Do not serve tuna with mayonnaise, which is fatty and often contains ingredients dogs do not need. Skip anything from a tuna salad or casserole, since those usually contain onion, garlic, or heavy seasoning. Avoid raw tuna, which carries a parasite risk on top of its mercury load. And never feed tuna alongside cooked fish bones, which can splinter. Plain, drained, and unseasoned is the whole recipe.
Risks and what to watch for
The main long-term risk is mercury accumulation from feeding tuna too often, which is why frequency matters more than any single serving. The short-term risks come from the extras: salt from brine or added seasoning can lead to excessive thirst and, in large amounts, sodium poisoning, while oil-packed tuna can cause an upset stomach or trigger pancreatitis in sensitive dogs. Tuna is also not a complete or balanced food, so it should never crowd out a proper diet. On rare occasions a dog can be allergic to fish, showing itchy skin, ear trouble, or digestive upset after eating it.
If your dog sneaks a modest amount of plain tuna, there is usually no cause for alarm. Offer fresh water and watch for any vomiting or diarrhea over the next day. If your dog ate a large quantity, especially salted, oil-packed, or seasoned tuna, or tuna mixed with onion or garlic, or if you notice tremors, weakness, or unusual thirst, call your vet or a poison control line. Reach the Pet Poison Helpline at 855-764-7661 or the ASPCA Animal Poison Control Center at 888-426-4435.
Safer fish and protein alternatives
If your goal is the omega-3s and lean protein that make fish appealing, there are lower-mercury options that are better suited to regular feeding. Salmon is rich in the same omega-3 fatty acids and, when fully cooked and boneless, makes an excellent occasional protein. Sardines are small, short-lived fish that carry far less mercury than tuna, and canned sardines in water are a convenient, dog-friendly choice in small amounts. Both give you the fish benefits without leaning on the one fish that stacks up mercury the fastest.
Soft training treats made with real pumpkin and blueberries, small enough to hand over often within the 10% treat rule.
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Frequently Asked Questions
Can dogs eat canned tuna in water every day?
No. Even water-packed, no-salt tuna should not be a daily food because mercury builds up with frequent feeding. Keep it to an occasional small serving, and if you want a fish your dog can have more regularly, choose sardines instead.
How much tuna can a dog eat in a week?
For most dogs the honest answer is little to none in a typical week. Tuna is an occasional treat, so a small drained spoonful now and then is plenty, and going a week or more between servings is a good habit. Small dogs should have the least, since the same amount is a larger dose for their body weight.
Can dogs eat tuna in oil or sunflower oil?
It is best avoided. The added oil is extra fat that can upset your dog's stomach and, in sensitive dogs, contribute to pancreatitis. Always pick tuna packed in water and drain it well rather than serving any oil-packed version.
Can dogs eat tuna with mayo?
No. Tuna mixed with mayonnaise is fatty and offers nothing your dog needs, and prepared tuna salad often contains onion or garlic, both of which are toxic to dogs. If you share tuna, keep it plain and drained with nothing added.
Is raw tuna safe for dogs?
Raw tuna is best avoided. It can carry parasites and bacteria, and raw fish exposes your dog to mercury without any benefit over a small amount of plain cooked or water-packed tuna. If you feed tuna at all, cook it plainly or use tuna canned in water.
Bottom line: plain tuna canned in water is safe for dogs as an occasional, drained, unsalted treat, but mercury and sodium keep it firmly off the everyday menu. Choose water over oil or brine, keep portions small and spaced out, skip anything seasoned, and lean on lower-mercury fish like salmon and sardines when you want a regular fish option. Fed with those limits in mind, tuna is a fine now-and-then snack rather than a staple.
Sources
Reviewed by the Webvet Veterinarian Team
General guidance based on credible veterinary sources — not a diagnosis or a substitute for your veterinarian. If your pet ate something toxic or is unwell, contact your vet or a pet poison line right away.