"Nepenthes muluensis" grows in nutrient-deficient soils of the upper montane zone. It typically occurs in open areas of mossy forest amongst ridge-top vegetation. On Mount Mulu, the species seems to be restricted to the western ridge and occurs from an elevation of around 1900 m to the summit at 2376 m. The summit vegetation is greatly stunted, rarely exceeding a metre in height. It is dominated by rhododendrons (particularly "Rhododendron ericoides"), as well as species of the genera "Diplycosia" and "Vaccinium". "Nepenthes muluensis" is most abundant in summit heath forest, where it forms dense stands with hundreds of white-speckled pitchers suspended over the sympatric shrubs.