The present paper is the outcome of an extensive floristic survey conducted in two phases by the authors in Kyongnosla Alpine Sanctuary, East Sikkim, India. During the study 411 taxa (400 species, 04 subspecies and 07 varieties) belonging to 173 genera and 54 families were recorded. The most dominating family was Asteraceae with 44 species followed by Ericaceae 28 species, Ranunculaceae 26 species, Polygonaceae 24 species and Rosaceae 20 species. These five families represent 34.13% of the total taxa recorded from the sanctuary. About 12 families were represented by only one species each. The most dominating genus was Rhododendron (18 species) followed by Primula (16 species), Pedicularis (15 species), Gentiana (11 species), and Impatiens (10 species). Among the different growth forms, herbs contributed the maximum (86.61 %) followed by shrubs (7.79%), trees (4.87%), climbers 0.49%, and epiphyte (0.24%).