The Thresher is so named for its distinctive tail with an extremely long upper lobe, and very short lower lobe. This large tail is used to "thresh" and stun its prey. The eyes are large, but not as large as the Bigeye Thresher, which as huge elongated eyes set high on the head, enabling it to see upwards.

The color varies, generally brown to grey brown along the upper body, and creamy to white below.

Threshers can grow to be 20 feet and 1000 lbs. They prefer cooler surface waters and feed on all kinds of schooling fish, such as mackerel and bunker.