We describe Dixonius sambhupura sp. nov. from the western bank and Koh Klap (island) of the lower Mekong River in Kratie Province, northeastern Cambodia. The new species differs from all currently recognized Dixonius by the following combination of morphological characters and pattern: maximal known snout-vent length of 49.0 mm, 14 or 16 longitudinal rows of dorsal tubercles; 34 to 37 paravertebral tubercles; 24 to 27 longitudinal rows of ventral scales across the abdomen; six precloacal pores in males, no pores in females; no marked canthal stripe; strongly barred lips; and a spotted to blotched dorsal pattern in adult males and females. We provide a cranial osteological description and a phylogenetic analysis of the new species. The discovery of this new species endemic to Cambodia brings the number of recognized Dixonius species to 20