Can Cats Eat Tuna?

Updated 18 October 2026 · Researched against PDSA, Cats Protection and International Cat Care guidance

Cats love tuna because it is strong-smelling and rich, not because it is good for them. A small amount of plain tuna in spring water, as an occasional treat, is harmless for most cats.

The problem is diets built on it. Tuna is not nutritionally complete: fed as a staple it causes thiamin deficiency and, in some cats, a painful inflammatory condition of body fat. Tuna in brine or oil adds salt and oil that a cat does not need, and larger fish carry mercury.

What to watch for in the UK

• Spring water, not brine or sunflower oil — and drain it before serving.
• A teaspoon as a treat, not a bowl as a meal.
• Never use tuna as the main food, even for a fussy cat — ask your vet about a proper appetite stimulant approach instead.
• Tuna with onion, mayo or pasta salad is a different hazard; see the onion page.

If your cat has already eaten it

1. A small amount of plain tuna: nothing to do.
2. A whole tin of brine or oil: offer water and watch for vomiting or diarrhoea.

Out of hours, use your practice's emergency number. If you can, take the packaging with you — the ingredient list often tells the vet more than the description does. This page explains risk; it cannot diagnose your cat, and it deliberately contains no doses or home treatments.

If your cat is already vomiting, see the cat vomiting guide. For the wider red-flag checklist, use sick cat symptoms. If a plant rather than a food is involved, the toxic plants checklist is the right page.

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