As its name suggests, N. muluensis was originally known only from Mount Mulu. Since its description it has also been found on several other mountains in Sarawak (including Mount Api, Mount Murud, and Bukit Batu Lawi) and one in southwestern Sabah. Nepenthes muluensis has not been recorded from the nearby summit of Mount Benarat, although this is a limestone peak and mostly lies outside the known altitudinal distribution of the species, which is 1700 to 2400 m above sea level.