Tuna (canned) — Food safety facts
Feed with care · Dogs · full breakdown on the linked food page
Occasional small amounts in water (not oil, not seasoned) are okay. Mercury builds up — do not feed regularly, especially to cats.
Short answer
Yes, but only a very small amount occasionally and it must be packed in water with no added salt or oil. Tuna contains mercury, which can build up in your dog's system over time, so regular feeding is not recommended. Watch for any signs of digestive upset after sharing, and if you notice vomiting or diarrhea, stop feeding it and check in with your vet.