Rapid Biodiversity Survey assessment was carried out along the sampling path of Lhonak Valley in the north district of Sikkim in October 2018 and a total of 102 floral species were recorded out of which, 81 species were represented by herbs and 21 species by scrubs. These species belonged to 55 genera in total (48 dicots, 4 monocots and 3 gymnosperms) and 33 families (27 dicots, 3 monocots and 3 gymnosperms). Out of the 102 species, 88 were dicots (86.3%), 11 were monocots (10.8%) and only 3 were gymnosperms (2.9%). Asteraceae was the largest family which contributed 11 species followed by Rosaceae (8 species), Gentianaceae (7 species) and Ericaceae and Caryophyllaceae (6 species each). The life-form spectra of the region shows dominance of hemicryptophytes with 43.3% followed by chamaephytes (29.9%), phanaerophytes (13.4%), therophytes (7.2%) and crypotophytic geophytes (6.1%). The high percentage of hemicryptophytes shows the indication of high altitude area and cold climate. The survey also reported the presence of 14 faunal and 21 avi-faunal species through direct and indirect evidences.