Nepenthes muluensis is one of the smallest species in the genus. Pitchers of adult plants are less than ten cm long. It seems to be closely related to Nepenthes tentaculata, however can easily distinguished by its characteristic upper pitchers and the attachment of the leaves to the stem. While lower pitchers are brownish and the upper pitchers have a dark purple coloration with cream-white patches. The peristome, the area near the mouth and the lid usually are completely coloured cream-white.

The characteristic location is Gunung Mulu but the species has also been recorded from Gunung Murud.
Young plants grow on half shady spots between the summit vegetation of low shrubs, rarely more than 1 m high. Later in the plants climb through these shrubs and form masses of upper pitchers on top of the shrubs which makes a spectacular sight.

Nepenthes muluensis is not an easy grower because it is very slow and requires typical highland conditions with lots of light and cool nights.