Sesame is one of the most important and oldest crops and most likely the oldest oilseed in the world. Sesame seeds contain 25% protein and 50% oil. During their growth, plants face many environmental stresses. Each of these stresses can have different effects on their growth, metabolism and function depending on the level of sensitivity in the growth stage of the plant species. Drought stress is considered to be one of the most important environmental factors that reduce the growth and performance of many agricultural plants, especially in arid and semi-arid regions of the world. Drought reduces the rate of photosynthesis and metabolism of carbohydrates in leaves, and these two processes lead to a decrease in the availability of assimilates for transfer to the organs of the reserves in the plant, and finally, an increase in organ abortion. In order to investigate the effect of drought stress on seed yield in a single plant as well as the morphological, phenological and biochemical characteristics in sesame cultivars, an experiment in the form of a randomized complete block design with three replications, in two separate environments in the crop year 2018-2019 in the research farm of the Faculty of Agriculture and natural resources of the Persian Gulf University has been done. The experiment included two normal environments and drought stress (50%) and 21 cultivars and lines. The results of the composite variance analysis of the measured traits showed that there is a significant difference between the cultivars and between the environments in terms of all the traits, including the traits of thousand seed weight and chlorophyll index. Cultivar × environment interaction for the traits of stem diameter and oil content at the five percent probability level, and traits of seed yield per plant, number of seeds per capsule, thousand seed weight, capsule number, capsule length, internode distance, leaf area, secondary leaf, catalase , proline, peroxidase, chlorophyll a, chlo