The warty frogfish grows up to 15 cm (5.9 in) long. Like other members of its family, it has a globulous, extensible body, and the soft skin is covered with small dermal spinules. The skin is covered with numerous small, wart-like protuberances. Its large prognathous mouth allows it to consume prey its same size. The coloring of the body is extremely variable because they always tend to match their living environments.
Frogfishes have the capacity to change coloration and pigment pattern in few weeks. However, the dominant coloration goes from white to black, passing through a whole range of related nuances such as cream, pink, yellow, red, and brown, often with dark, circular spots and/or with saddles. Some heavily spotted specimens can easily be confused with its closed relative Antennarius pictus. This characteristic can help to separate them: usually, A. maculatus has red or orange margins on all fins and sometimes a spike of the saddle blotch start posterior to the eye