The alpine vegetation of the Sikkim Himalaya has received limited attention despite being a part of the Eastern Himalaya global biodiversity hotspot. The current study undertaken in the third highest landscape in the world—the Khangchendzonga National Park (KNP)—provides information on the different alpine vegetation communities and aspects of their ecology. The transverse spurs from the unique north–south Khangchendzonga range result in a landscape level differentiation of the Outer, Inner, and Tibetan Himalaya in just 50 km. The alpine vegetation based on numerical classification has been segregated into 11 types with the extensive ones being Juniperus indica scrub, Rhododendron scrub, Kobresia duthiei moist meadow, Kobresia nepalensis moist meadow, Kobresia pygmaea dry meadow, and Anaphalis xylorhiza mixed meadow. Based on Canonical Correspondence Analysis, the 3 environmental gradients of rainfall, elevation, and soil were found to be the primary determinants of vegetation patterns. A total of 585 species of angiosperms belonging to 67 families and 243 genera were recorded in a 390-km² area. Compared to the Western Himalaya, proportions of alpine scrub and sedge meadows were higher, whereas herbaceous formations and grassy meadows were limited in extent. The alpha species diversity was found to be lower mainly because the alpine region here is partly isolated, narrower, fragmented, and dominated by a depauperated scrub zone.