Located in the extended buffer zone of Nanda Devi Biosphere Reserve in Western Himalaya, Niti valley represents a cold arid region. The reserve has been extensively surveyed in terms of floral diversity by various workers, albeit highly confined to the core zones. The current survey recorded 495 species belonging to 267 genera and 73 families of vascular plants through systematic collection in the years 2011, 2012 and 2014. Of the recorded species, 383 were dicots, 93 monocots, 9 pteridophytes and 10 gymnosperms. Asteraceae was most diverse family (32 genera with 58 species), followed by Poaceae (22 genera with 41 species), Lamiaceae (15 genera with 19 species) Fabaceae (14 genera with 22 species), Brassicaceae (12 genera with 12 species) and Rosaceae (11 genera with 36 species). The present survey also updates the existing flora of Nanda Devi Biosphere Reserve (801 species) with addition of 167 species. This study reveals that the Niti valley forms a transition zone, as the floral elements have affinity with Trans as well as Greater Himalaya.