We assessed distribution and abundance of mammals in dense, rugged eastern Himalayan habitats of Khangchendzonga Biosphere Reserve (BR), Sikkim, India, from April 2008 to May 2010, using field methods and remote cameras under varying rain and snow conditions. We report the occurrence of 42 mammals including 18 species that have high global conservation significance. Three leopards ( Panthera uncia, Panthera pardus, Neofelis nebulosa ), Tibetan wolf ( Canis lupus chanco ), wild dog ( Cuon alpinus ), red panda ( Ailurus fulgens ), Asiatic black bear ( Ursus thibetanus ), and two musk deer species ( Moschus chrysogaster, M. fuscus ) were recorded. Species number decreased with increasing elevation, 22 were recorded in temperate habitats, 18 in subalpine and 11 in alpine. The yellow-throated marten ( Martes flavigula ) and black bear were found to have the most diverse distribution extending from temperate to alpine. Red fox ( Vulpes vulpes ) was the most abundant carnivore (8.98±2.31 photo capture/100 days) while goral ( Naemorhedus goral ) was the most abundant prey (9.14±5.27). Camera trap detected most of the mammals of the intensive study area (35/39). Considering the benefits and limitations, we recommend application of camera trapping along with sign surveys for monitoring of mammals in Khangchendzonga BR for effective conservation.