It is a streamlined, fast-swimming pelagic fish, common in tropical waters throughout the world, where it inhabits surface waters in large shoals (up to 50,000 fish), feeding on fish, crustaceans, cephalopods, and molluscs. It is an important prey species for sharks and large pelagic fishes and is often used as live bait when fishing for Marlin. It has no scales, except on the lateral line and the corselet (a band of large, thick scales forming a circle around the body behind the head). It commonly reaches fork lengths up to 80 cm (31 in) and a weight of 8–10 kg (18–22 lb). Its maximum fork length is 108 cm (43 in) and maximum weight is 34.5 kg (76 lb). Ageing skipjack tuna is difficult, and the estimates of its potential lifespan range between 8 and 12 years.
Skipjack tuna is a batch spawner. Spawning occurs year-round in equatorial waters, but it gets more seasonal further away from the equator. Fork length at first spawning is about 45 cm (18 in). It is also known for its potent smell.