Treeline migration on account of climate change have been reported from various forest ecosystem of the world. The Himalaya are no exception to this. Meteorological records from the western Himalaya, show increasing trend in mean annual temperature in the last century with rapid winter warming. The forest vegetation at the ecotone zone are sensitive to changes in climate variability having profound effects on species composition and diversity, recruitment pattern and altitudinal shifts. We carried out dendrochronological study to investigate the treeline migration and BAI in the treeline ecotone region at Tungnath, Uttarakhand, western Himalaya at an elevation of 3300 m asl. The tree cores (n=125) were collected from the dominant Abies spectabilis (Himalayan fir) and standardised. The response function analysis between ring-width index and climate variables (temperature and precipitation) shows temperature of the winter months are conducive for tree growth. Precipitation of previous year November and current year February is significant predictor of tree growth in the region. BAI shows increasing trend from 1950 AD to late 20th century. The treeline have been reported to have upward migration at ~7.6 m per decade attributed largely due to increased temperature trend over the region. However, the shift rate fluctuates with altitudes and time period, it was ~2.46 m/year between 1636 and 1715 AD, ~3.95 m/year between 1715 and 1772 AD and 0.38 m/year between 1773 and 1907 AD.  Presence of only few seedling shows poor regeneration of Himalayan fir at the treeline ecotone largely due to the increased changes in land use patterns for the last few decades and thus future monitoring for overall growth and survival is needed.