Considering the rapid climatic changes in the past few years, the effect of high temperature on wheat productivity is global concern. Heat stress is one of the major abiotic stresses reducing wheat production. Heat stress reduces grain weight and number, chlorophyll content and photosynthesis activity. This study was carried out during two successive seasons 2018/2019 and 2019/2020 at Almatana agricultural Research Station, Luxor, Upper Egypt, to investigate the effect of two sowing dates 20th November (favorable sowing date) and 10th January (late sowing date, after sugarcane harvest) on yield characters, of twenty bread wheat genotypes. The objective was to understand heat stress effects on grain yield and its components to estimate some selection indices for heat tolerance in wheat. The studied characters were number of spikes/m2, number of kernels/spike, 1000-kernel weight and grain yield (ton/ha). Results indicated that sowing dates and genotypes had significant effects for all studied characters. Delaying sowing date after sugarcane harvest reduced no. of spikes/m2, no. of kernels/spike, 1000-kernel weight and grain yield by an average of 31.62, 32.85, 32.76 and 37.74%, respectively, compared to the favorable sowing date. Highest grain yield (8.81) t/ha under favorable sowing date was for gemmeiza11, while shandaweel1 gave (5.92) t/ha the highest grain yield under late sowing date. Heat susceptibility index (HSI) over all two seasons ranged from 0.78 for Shandaweel1, to 1.23 for genotype Line8.