The present investigations were undertaken in the Department of Forest Products, College of Forestry, Dr YS Parmar University of Horticulture and Forestry, Nauni, Solan, HP to study the effect of light and temperature on germination behaviour of Aconitum deinorrhizum, an endangered medicinal plant of the Western Himalaya. The study revealed that the seeds of A deinorrhizum exposed to continuous light conditions gave better responses in terms of initiation of germination, days taken for completion of germination and seed germination percentage as compared to continuous dark condition irrespective of the temperatures. Maximum germination percentage of 76.67 was observed in seeds maintained at 200C under continuous light conditions. Under continuous dark conditions seed maintained at 200C also gave maximum germination (63.60%). Exposure to 200C temperature at continuous light also gave peak value (2.17), germination value (4.58) and germination energy (30.14%) indicating, thereby, that 200C temperature is the most optimal for getting higher seed germination in this species.