This paper explores the determinants of environmental sustainability in Nepal. Carbon intensity has been used as an alternative to measure environmental sustainability. Using the auto regressive distributed lag model (ARDL) based on timeline data for the period 1984 to 2014 the study concludes that economic globalization, urban population growth, GDP per capita growth and energy consumption have a significant and positive impact on carbon intensity in the long run. The outcome justified by the diagnostic tests shows the threat to the environmental sustainability in Nepal as all the selected variables are found increasing total carbon intensity.Without sincere and grass-root effort such negative impact on the environment through reduction in carbon intensity seems impossible in the present context of slow industrial development. Based on the outcome the study suggests for the sector-wise carbon intensity reduction strategy. It further demands for the in-depth research and development on determinants of carbon intensity for the effective implementation of climate change policy as well as for promoting green economy as envisioned in 15th five year plan of government of Nepal.