Defoliation causes significant production losses in sesame. However, the varied reactions in relation to the phenological stages are not known. Therefore, the present study aimed to determine the most sensitive phenological stages. Thus, three varieties were subjected to 50 % defoliation at three phenological stages in a complete randomized block trial with three repetitions of 12 treatments. The analyses of variance carried out on the data recorded at the end of the cycle showed that the values ​​of six of the seven parameters studied were different according to the variety of sesame and the phenological stage of the defoliation application. Thus, overall, the plants defoliated at the vegetative stage presented the lowest value for the number of bolls per plant (84), the mass of dry grains per plant (4.48 g) and the yield (597.082 to 1066.677 kg / ha). Also, plants defoliated at the beginning of flowering presented the lowest average value for three vegetative parameters: plant height (126.90 cm), stem diameter (10.04 mm), length of the shortest branch (0.47 cm). Consequently, plants defoliated at the start of flowering have the greatest average mass of dry grains, except in the cultivar Benais Gbè from Ladoué. Similarly, plants defoliated at the start of fruit set presented the highest average value for four of the six parameters. These latter results indicate that 50 % defoliation at the vegetative and early flowering stage decrease production and growth, respectively. They are useful for more efficient integrated management of farms.