The microscopic characteristics of dorsal guard hairs of the Namdhapa flying squirrel Biswamoyopterus biswasiwere examined using the optical light microscope at the Zoological Survey of India during May 2016. The unique microscopic characteristics such as ‘multicellular’ and ‘multiserial ladder’, the structure of medulla and ‘biconvex’, shape of the cross-section of dorsal guard hair determines the species identity of B. biswasi. The high-resolution photo-micrographs and key characteristics of hair presented here can be used as an appropriate reference for species identification.