Nepenthes dubia was for a long time thought to be endemic to Mount Talakmau, but it was recently found on a second mountain, where it grows at lower elevations of around 1600 m above sea level. On Mount Talakmau, the species occurs at an altitude of 1800-2700 m. At lower elevations on Talakmau, it grows epiphytically in montane forest. However, above around 2400 m, vegetation is very stunted and here N. dubia also grows terrestrially on clumps of moss.