Pyriproxyfen (Admiral) is an insect growth regulator (IGR) acts as anti- juvenile hormone. The present work aims to investigate the toxicological effect of Pyriproxyfen on both sexes of rust red flour beetle, Tribolium castaneum resulted from treated 4^th larval instar with LC₅₀ value (2.4ppm) and its effect on female production and male's perception to pheromone. The results indicated that both treated and untreated sexes could secrete a pheromone that was able to stimulate the opposite sex as well as its own sex. But production and responsiveness of pheromone in untreated groups were significantly higher than treated one. Females secreted a pheromone is a sex pheromone, While the pheromone secreted by males is an aggregation pheromone