Werneria mertensiana is a species of toad in the family Bufonidae. It is found in western Cameroon (Mount Nlonako, Mount Manengouba, Mount Kala, possibly Western High Plateau) and possibly in the Obudu Plateau in Nigeria. It is typically found associated with rocks in streams and waterfalls in forest and degraded secondary habitats at the lower limit of the submontane zone, 800–1,050 m (2,620–3,440 ft) above sea level. It can also be found in leaf-litter away from water. It can be locally relatively abundant. The main threat to it is probably habitat loss.