An investigation was carried out with forty greengram genotypes including one check Samrat during summer 2015 to find out suitable selection indices for influencing the performance of genotypes under heat stress. Seed yield showed positive and significant association with days to maturity (DM), growing degree days (GDD), relative temperature depression (RTD) and heat use efficiency (HUE). Stepwise regression analysis showed that maximum contribution was made by HUE followed by photothermal index (PTI) and DM. This indicated that HUE might be utilized as primary key factor, whereas PTI, DM and RTD might be utilized as secondary key factor for improving heat tolerance in greengram. The comparison of different functions revealed that among the single character selection index HUE (index IV) was the key component to construct selection index for terminal heat tolerance in greengram. Besidethis DM, PTI, RTD, HUE and seed yield per plant (SYP) (index XV) should be simultaneously selected to achieve maximum gain and improve the heat tolerance in greengram.