This study aimed to performed divergent phenotypic selection for 1000-kernel weight (1000-KW) under heat stress in a population of 140 F₈ recombinant inbred lines (RILs) derived from a cross between tolerant and susceptible landraces of bread wheat (Triticum aestivum L.). Correlated responses to selection for grain yield per plant, cell membrane thermostability (CMS) and reduction in tetrazolium chloride (TTC) traits were also measured. Grain yield per plant was evaluated in the field at both optimal and late sowing dates, while CMS and TTC were assayed at seedling stage. Highly significant responses to selection were obtained for 1000-KW in both high (9.76%) and low (4.64%) directions. Realized heritability for 1000-KW (h²= 0.28) was similar to those calculated from the parent-offspring regression (b_po= 0.29). Selection for low 1000-KW produced highly significant and positive correlated responses for grain yield per plant (7.95%), CMS (17.24%) and TTC (36.74%), whereas selection performed for high 1000-KW only produced a highly significant and positive correlated response for grain yield per plant (9.74%). Highly significant and positive correlation coefficients were found between 1000-KW with grain yield per plant (r= 0.54, P<0.01), CMS (r= 0.31, P<0.05) and TTC (r = 0.52, P<0.01). Grain yield per plant was also significantly and positively correlated with CMS (r= 0.31, P<0.05) and TTC (r= 0.69, P<0.01). A highly significant and positive correlation was also observed between CMS and TTC (r= 0.40, P<0.01). Out of five simple sequence repeats (SSR) and three inter simple sequence repeats (ISSR) markers used to screen ten RILs selected for 1000-KW, two SSR (Xgwm456 and Xwmc596) and a single ISSR (HB-13) markers were specific for 1000-KW. These markers could be considered as reliable markers for heat tolerance in wheat breeding programs.