Tuna tartare is a dish made from raw tuna that has been cut into small pieces before serving. It can be chopped, cut into chunks, or sliced. Often, tuna tartare is flavored by adding oils, spices, and other flavorings, but sometimes it is simply cut up raw tuna served in an attractive presentation. It is frequently served with crackers, chips, or toast, allowing the diner to spread the soft raw fish on the crunchy breaded item. Tuna served tartare style is similar to tuna sashimi, except that sashimi is more often cut into evenly sized slices or chunks.

This dish can be served in several ways. At a party, it might come in a serving dish with a spoon meant to dole out single servings on each guest's plate. It can also be served on pre-prepared crackers with the tuna and ingredients piled on top. At restaurants, it is often served in a visually appealing manner, usually shaped atop greens or sauces meant to complement the flavor of the dish.

In addition to the tuna meat, tuna tartare can also include other soft fruits and vegetables mixed in with the cut tuna. Common vegetable flavors combined with tuna in a tuna tartare include avocados, onions, and cabbage. It can also be mixed with caviar, roasted nuts, and toasted sesame seeds. When it is served with caviar, tuna tartare is usually presented on top of a cracker, often an Asian-style cracker like a sesame cracker or fried wonton chip.

Sometimes, partially cooked tuna is used in a tartare, if it comes in the form of seared ahi. Ahi is one name for a variety of tuna called the yellowfin tuna. A popular way to serve ahi is to sear it, which means to cook it quickly at a high heat, before it is sliced and served. Searing ahi means that the outside of the fish is cooked to a crisp, while the warm inside remains raw. This is a common fish preparation that can make raw fish more palatable to picky eaters, and it can help introduce an otherwise squeamish eater to raw fish.

Tuna tartare is not the only dish that has pieces of raw tuna in it. It is a cousin to the popular marinated fish dish called a ceviche. Like tuna tartare, ceviche includes marinated raw fish mixed with other ingredients. The difference between a tuna ceviche and tuna tartare is that ceviche fish is marinated in citrus, which changes the texture and flavor of the fish. Texture changes in the fish cause citrus marinated fish to seem more cooked, though it is still raw.