It is endemic to humid premontane slopes of the Cordillera de Talamanca in Costa Rica and western Panama.

[1][2] Isthmohyla lancasteri was described by Thomas Barbour in 1928, based a single specimen (the holotype) collected by C. R. Lancaster—and after whom the species is named.

The ventrum is greyish white and may have dark mottling, depending on locality.

[3] Isthmohyla lancasteri live in humid lowland and montane forests at elevations of 368–1,200 m (1,207–3,937 ft) above sea level.

There is some habitat loss (deforestation) occurring in its range but the species is not considered threatened by the International Union for Conservation of Nature (IUCN).