We describe a new species of diurnal gecko, Gonatodes castanae sp. nov. from the foothills of the Serranía de San Lucas, municipality of Norosí, Department of Bolívar, Colombia. The new species differs from all species in the genus by the combination of the following characters: moderate size, subcaudal scale pattern type B (1’1’1’’), typically two rows of lateral scales on the digits, and aspects of color pattern in males (dorsum, flanks, limbs and tail with white ocelli on a black background) and females (dorsum, flanks, limbs and tail with brown to black reticulations and withe spots on a greenish-yellow background). The validity of the new species is also supported by molecular analyses. This species inhabits relicts of riverine forests at about 150 m above sea level (a.s.l.). Gonatodes castanae increases the number of known species in this genus to 34 and the species registered for Colombia to eight.