The Tokay Gecko is the second largest Gecko species, attaining lengths of about 11–20 inches (28–51 cm) for males, and 7–19 inches (18–48 cm) for females, with weights of only 150–400 grams (5.3–14.1 oz). They are distinctive in appearance, with a bluish or grayish body, sporting spots ranging from light yellow to bright red. The male is more brightly colored than the female. They have large eyes with a vertical slit pupil. Eyes are brown to greenish brown and can be orange or yellow.
Males are very territorial, and will attack other male Tokays as well as other Gecko species, as well as anything else in their territory. They are solitary and only meet during the mating season. Females lay clutches of one or two hard shelled eggs which are guarded until they hatch. Tokay Geckos feed on insects and small vertebrates. Their strong bite is needed to crack the shell of hard cockroaches that live in the rainforests. They are also an extremely strong climber and their foot pads can support their entire weight on a vertical surface for a long amount of time without any effort. Compared to other gecko species, the Tokay has a robust build, with a semi-prehensile tail, a large head and muscular jaws; though common in the pet trade, Tokays are reputed to be capable of inflicting a painful bite, making them ill-suited for inexperienced keepers.
Their mating call, a loud croak, is variously described as sounding like token, gekk-gekk or Poo-Kay where both the common and the scientific name (deriving from onomatopoeic names in Malay, Sundanese, Tagalog, Thai, or Javanese), as well as the family name Gekkonidae and the generic term gecko come from. The call is similar to the call made by Gekko smithii (Large Forest Gecko).