Two field experiments were conducted at El-Gemmeiza Agricultural Research Station, Agricultural Research Center, Egypt in 2018 and 2019 seasons to study the physiological effects of benzyl adenine (BA) on growth, boll setting and productivity of cotton plant cv. Giza 86. Date, number of applications and four concentrations of BA were examined used a split-plot design with three replicates.Sprayings of BA three times increased estimated elements and photosynthetic pigments in leaves in 2018 season, growth traits (except number of fruiting branches), while two sprays significantly increased number of fruiting branches, earliness measurements (except boll shedding% which decreased), seed cotton yield feddan^-1 and open bolls number plant^-1 in both seasons.BA at the medium level (40 ppm) gave a significant increase in the numbers of fruiting branches, total and open bolls plant^-1, percentages of boll setting and earliness as well as seed cotton yield feddan^-1 in both seasons compared to the rest of treatments. The high level of BA gave a significant increase in studied elements content of leaves and photosynthetic pigments in 2018 season and growth traits with the exception of fruiting branches. Control treatment (sprayed with tap water) gave the lowest values in this respect with a significant increase in boll shedding %. Fiber traits were not significantly affected by the two factors studied and their interactions. It could be concluded that spraying with BA at 40 ppm two times under El-Gemmeiza conditions reduces the undesirable shedding and increases bolls setting which leading to an increase in cotton productivity.