A plain olive, in small amounts, is fine
Yes, dogs can eat olives in moderation, provided the olive is plain and the pit is gone. Green and black table olives are not toxic to dogs, and their flesh carries fats that explain why dogs find them so interesting at the table. The catch is everything that comes with the olive: the salty brine it swam in, the hard pit at its center, and whatever a deli stuffed inside it. Treat an olive as an occasional shared bite, never as a handful tipped from the jar.
The pit is the real hazard
An olive pit is exactly the size to lodge in a small dog's throat and exactly hard enough to crack a larger dog's tooth when he crunches down expecting soft flesh. Swallowed pits can also irritate or block the gut as they travel through. Pitting takes seconds: press the olive under the flat of a knife or use a cherry pitter, then slice the flesh so even a greedy dog cannot gulp a whole round piece. Never hand a dog an olive straight from a salad or a pizza where you cannot be sure the pit is out.
Brine, oil, and stuffings change the answer
Olives packed in brine deliver far more salt than a dog needs in a treat, and a dog who laps the jar liquid or eats several brined olives may drink heavily and end up with an upset stomach. Rinsing a pitted olive under water knocks off much of the surface salt. Stuffed olives are a different food altogether: garlic fillings, chili, anchovy paste, and cheese all add ingredients or richness that can trouble a dog, and cocktail olives marinated in alcohol-based mixes should never be shared at all.
How many olives make sense
For most dogs, one olive, pitted and cut up, is a complete treat. A very large dog might handle two without issue, but olives are calorie-dense for their size, and dogs who are watching their weight or who have a history of pancreas trouble after fatty foods should skip them entirely. If olives are new to your dog, offer a small piece first and wait a day to see how his stool and appetite look before making them an occasional habit at antipasto night.
When an olive snack needs a vet call
Contact your veterinarian if your dog swallowed a pit and then gags, drools, paws at his mouth, vomits, or stops eating, because a lodged or swallowed pit deserves professional eyes. Call as well if he helped himself to a bowl of cocktail olives or a large quantity of brine and develops vomiting, diarrhea, or unusual thirst. Mention any stuffing involved, since garlic-heavy fillings change what the vet will want to monitor during the visit or phone consultation.
Passing the pitted-only rule to everyone
Olives appear at gatherings where several people feed the dog from their plates, each assuming someone else checked the pit. A written treat note ends that guessing. In KinsLe, Care Teams lets you record that olives are allowed only pitted, rinsed, and cut up, so the person making the holiday antipasto platter and the person feeding dinner later both follow the same simple rule for your dog.