With caution — cats and canned sardines
Sardines in springwater are one of the better fish treats for cats — high in omega-3s, good protein, and genuinely palatable. Sardines in brine are too high in sodium to be safe. Sardines in oil add unnecessary fat and the oil type matters. Check the label before opening the tin.
🏆 Pet Care Community Safety Score™ — Canned Sardines for Cats
"Sardines in springwater are on my short list of human foods I actively recommend for cats. The omega-3 content — EPA and DHA — is genuinely beneficial for coat condition, joint inflammation, and kidney health, and sardines are lower in mercury than tuna or larger fish species. The sodium in brine-packed sardines is the disqualifier: a standard 95g tin in brine contains around 300–400mg of sodium, which is too high for regular cat feeding. Springwater tins are a completely different product from a safety perspective."
The straight answer
Sardines in springwater are a genuinely good treat for cats — among the better fish options available at Australian supermarkets. The omega-3 fatty acids are beneficial, the protein is high quality, the bones are soft and digestible, and cats love them. The entire safety question comes down to the liquid they're packed in: springwater is fine, brine is not, and oil is somewhere in between depending on the type and quantity.
Why the packing liquid matters so much
A standard supermarket sardine tin from Coles or Woolworths contains either springwater, brine (salt water), or vegetable oil. The sardine inside all three tins is nutritionally similar. The liquid changes the sodium and fat load dramatically.
Springwater: Minimal added sodium, no added fat. This is the version to buy. A 95g tin of sardines in springwater contains roughly 200–250mg of sodium — still meaningful for a cat, but divided across 2–3 servings over a week, well within safe limits.
Brine: Brine is concentrated salt water. The sardines absorb sodium during the packing process, and the fish itself ends up significantly higher in sodium than springwater-packed sardines. A 95g tin in brine can contain 350–500mg of sodium. Draining the liquid does not remove the sodium that has been absorbed into the fish. Not safe for regular cat feeding.
Oil: Sardines in oil (sunflower, soybean, olive) add a fat load that a cat does not need in a treat context. The omega-3 benefit of the sardine is partially offset by the omega-6 in the packing oil, which affects the overall fatty acid balance. If springwater is unavailable and oil is the only option, drain very thoroughly and feed occasionally rather than regularly. Olive oil sardines are the most commonly available and the least problematic of the oil options — but they are still a compromise.
The omega-3 argument
Sardines are one of the richest practical sources of long-chain omega-3 fatty acids — specifically EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These are relevant to cats because:
- Coat condition: EPA and DHA reduce inflammatory mediators that contribute to dry, flaky skin and dull coat. In clinic, I see a noticeable difference in coat quality in cats supplemented with fish-source omega-3 compared to those on omega-3-poor diets.
- Kidney health: Omega-3 supplementation is associated with reduced proteinuria and slowed progression of chronic kidney disease (CKD) in cats. Given that CKD affects an estimated 30–40% of cats over 12 years old in Australia, this is a clinically relevant consideration.
- Joint inflammation: EPA specifically has documented anti-inflammatory effects on synovial joint tissue, relevant for arthritic older cats.
A single sardine 2–3 times per week provides a meaningful omega-3 supplement without the mercury accumulation risk associated with larger, longer-lived species like tuna or salmon.
Sardine bones — fine to eat, actually beneficial
Unlike cooked chicken or beef bones, sardine bones are small, soft, and fully digestible. They do not splinter. A cat eating a whole sardine including the bones is consuming a good source of dietary calcium and phosphorus in an appropriate ratio. There is no need to debone sardines before feeding them to cats.
This is one of the advantages of small, short-lived fish species over larger fish for cat supplementation.
Steatitis — the risk with excessive fish feeding
Steatitis, also called yellow fat disease, is a condition caused by a deficiency of vitamin E combined with excessive dietary polyunsaturated fat. Fish — and particularly oily fish — is high in polyunsaturated fats (the same omega-3s that provide the health benefit). When these fats are fed in very large amounts without adequate vitamin E, they oxidise in body fat stores, causing inflammatory, painful nodules throughout the cat's subcutaneous fat.
This is not a risk from feeding one sardine twice a week. It is the historical presentation of cats fed canned fish as their primary diet — a feeding pattern common in the 1960s–80s before it was understood. Today, the practical risk is for cats fed fish as the dominant protein source rather than a supplement.
Signs of steatitis: painful response when touched along the body, visible or palpable lumpy deposits under the skin, lethargy, fever, loss of appetite. If you see this in a cat on a high-fish diet, veterinary assessment is needed.
Sardines vs. other tinned fish for cats
| Fish type | Safe? | Notes |
|---|---|---|
| Sardines in springwater | Yes | Best option — omega-3 rich, soft bones, low mercury |
| Sardines in brine | No | Too high sodium |
| Tuna in springwater | Yes (limited) | Mercury accumulation concern; low taurine; addictive |
| Tuna in brine | No | High sodium |
| Salmon in springwater | Yes | Good option; remove any larger bones |
| Anchovies in water | Sometimes | Naturally high salt — see dedicated anchovy guide |
| Sardines in tomato sauce | No | Sauce contains salt, tomato paste, often garlic |
| Mackerel in springwater | Yes | Similar to sardines; good omega-3 source |
🚨 My Cat Ate Canned Sardines — What Now?
Sardines are not a toxicity risk. If your cat ate sardines in brine and is showing excessive thirst, vomiting, or lethargy, call the Animal Poisons Helpline on 1300 869 738. For signs of steatitis (painful lumps under the skin, reluctance to be touched), contact your vet.
Signs that warrant a vet call:
- Digestive upset (vomiting
- loose stools) on first introduction. With very frequent feeding over weeks: signs of vitamin E deficiency (steatitis — painful
- lumpy fat deposits under the skin — caused by excessive polyunsaturated fat without adequate vitamin E). Steatitis is rare in cats fed fish as a supplement rather than a primary food
If your cat ate a large amount or is showing the signs above: Don't wait — call immediately.
📞 Animal Poisons Helpline: 1300 869 738Available 24/7 across Australia. Have your cat's weight, breed and approximate quantity consumed ready when you call.
Frequently Asked Questions
This is the same "tuna addiction" problem with a different fish. Cats can develop strong food preferences when one highly palatable food is offered repeatedly. Transition back to a complete cat food by offering a small amount of sardine mixed into a full meal rather than sardines alone, then gradually reducing the sardine proportion over 2–3 weeks.
For more on seafood safety for cats, see our cat food safety hub and our guide to can cats eat raw prawns for another species-appropriate protein option.
📚 Sources & Further Reading
- Loew FM, Martin CL, Dunlop RH. Naturally-occurring and experimental thiamine deficiency in cats. Can Vet J 1970;11(6):109-113.
- Munday JS, et al. Steatitis in cats associated with excessive dietary unsaturated fatty acids. N Z Vet J 2001;49(1):37-40.
- Cornell Feline Health Center — Nutritional Needs of Cats. https://www.vet.cornell.edu
- FSANZ — Seafood and Mercury in Australia. https://www.foodstandards.gov.au
- Australian Veterinary Association — Feline Nutrition Guidelines. https://www.ava.com.au
