Nepenthes mollis has only been collected once, on October 17, 1925 by Frederik Endert on Mount Kemul in East Kalimantan. The plant was collected near the summit of the mountain, at an elevation of approximately 1,800 m. It was discovered during an expedition to central Borneo by the Forest Research Institute of Bogor (then known as Buitenzorg), on which Endert also collected N. fusca for the first time.