A field experiment was conducted at Agronomy Farm, S.K.N. College of agriculture, Jobner, Jaipur, Rajasthan to evaluate the effect of sowing time, varieties and salicylic acid (SA) application on different physiological parameters (i.e. relative water content, photosynthetic rate, transpiration rate, stomatal conductance, leaf temperature, Membrane stability index, chlorophyll stability index, heat susceptibility index) of Indian mustard. The experiment was laid out in split plot deign and replicated thrice. The experiment consisted of three sowing dates [20^th October (timely sowing), 15^th November (late sowing) and 30^th November (very late sowing)], two varieties [RGN-236, RGN-229] and four levels of Salicylic acid (Control, SA 50 ppm, SA 100 ppm and SA 150 ppm). Physiological traits like relative water content, photosynthetic rate transpiration rate, stomatal conductance, leaf temperature, chlorophyll stability index Content, heat susceptibility index and membrane stability index are directly correlate with heat stress tolerance in crop plant. Results were revealed that effect of different sowing time, varieties and concentration of SA has shown significant effect on all tested physiological parameters of Indian mustard and those are associated with high temperature stress tolerance.