Three cycles of pedigree selection started in the F₂ were conducted during the four summer seasons of 2020 to 2023 to study the effect of single trait selection on genetic variability, heritability and improving seed yield of Sesame. The experiments were carried out at reclaimed loamy sand soil. The third cycle was evaluated in the reclaimed and clay soils. The selection criteria were plant height cm (PH), length of fruiting zone cm (LFZ), number of capsules plant^-1 (NCP), seed yield plant^-1 g (SYP), seed index g (SI) and oil%. The genetic materials were F₂, F₃, F₄ and F₅- generations of sesame (Sesamum indicum L.). The genotypic coefficient of variation (GCV%) decreased dramatically from the F₂-generation to F₅-generation. However, the remaining variability in NCP, SYP and SI was sufficient for further cycles of selection. Both of broad sense and narrow sense heritability's increased by selection towards homozygosity. Results indicated the ability of single trait in changing the mean selection criterion but adversely affects some correlated traits. Therefore, selection index combined favorable traits could be recommended. The genetic gain in SYP in percentage of the MP was 27.12% when selection practiced for SYP, followed by selection for NCP (19.65%), PH (17.31%) and SI (10.14%) in reclaimed soil. Otherwise, the order for improving SYP in clay soil was NCP (20.98%), LFZ (20.23%), PH (18.59%), SYP (17.38%) and SI (12.04%). The difference in the preference of selective traits under both sites of evaluation for SYP improvement is due to the interaction of family performance with the environment.