A hammerhead shark has a wide head shaped like a hammer. This wide, hammer-shaped head is called the cephalofoil, with a hammerhead's eyes at the two ends of it.

In a 2009 study the winghead shark, a hammerhead, had a 48-degree arc in front of it covered by both eyes. The same study found that the scalloped hammerhead has a binocular overlap of 34 degrees. The bonnethead, whose head is more spade than hammer, had a much smaller binocular overlap of 13 degrees. A report on the winghead's eye overlap said it must give the shark exceptional depth perception.

The wide-set eyes give a hammerhead good sight, and the hammerhead's wide head has been hypothesized to give it sensory advantages.

The great hammerhead is the biggest kind of hammerhead shark, and the front edge of an adult great hammerhead's head is nearly straight, with a head width that is less than 40% of its total length. A scalloped hammerhead has a notch in the middle of the front of its head.

A hammerhead has electrical sense organs called the ampullae of Lorenzini, which are small pores along the underside of its head. These pores are gel-filled and work as highly sensitive electrical receptors.

A hammerhead eats fish, squid and crustaceans such as crabs, and a great hammerhead favors stingrays, groupers and sea catfishes as food. Scalloped hammerheads use their hammer-like head to pin stingrays to the ocean floor before eating them.

Hammerhead sharks live in warm seas around the world. A great hammerhead lives close to the shore and also far out at sea, although it is often found near reefs and the bottom, in water 1 to 80 meters deep.

A study of great hammerheads in the western North Atlantic used pop-off archival satellite tags. In that study 75% of great hammerhead depth records were shallower than 30 m, although great hammerheads were found at significantly deeper depths during the daytime.

Adult scalloped hammerheads dive rapidly and repeatedly from warm surface waters to depths exceeding 800 meters, where the water is as cold as 5 degrees C. A scalloped hammerhead followed for 27 days made more than 76 deep dives at night, the deepest of which reached 964 m, where the water was 5.8 degrees C. The authors of that tracking study said the purpose of the nightly deep diving is unknown.

As of November 2026, the IUCN Red List lists both the great hammerhead and the scalloped hammerhead as Critically Endangered. Two distinct population segments of the scalloped hammerhead are listed as endangered and two as threatened under the US Endangered Species Act, in a final rule dated July 3, 2014.

A mother hammerhead gives birth to live pups, and a female great hammerhead breeds once every two years, with litters of 6 to 42 pups reported, each measuring 50 to 70 cm at birth. A mother scalloped hammerhead carries her pups for 9 to 10 months before they are born.

Scalloped hammerhead pups live in shallow coastal nursery areas and young scalloped hammerheads swim together in large schools. Adult scalloped hammerheads form schools in which the sexes are mostly kept apart, and adult males almost exclusively enter schools when in search of a mate.

Great hammerheads migrate with the seasons. The great hammerhead is described as a solitary, nomadic and migratory species. Scalloped hammerheads migrate with the seasons too, and some travel in large schools heading north for the summer.

Words to know

• binocular: using both eyes
• hypothesized: suggested
• nursery: young sharks' home
• solitary: living alone
• nomadic: wandering