Chlorfluazuron (Atabron) is an insect growth regulator (IGR) belongs to benzoylphenyl urea for controlling the major insect pests. The present work aims to investigate the toxicological and biological effects of Chlorfluazuron on the 4th larval instar of rust red flour beetle, Tribolium castaneum at different concentrations (0.1, 0.5, 1, 5 and 10 ppm) under laboratory conditions. The results revealed high significant mortality in larvae, pupae and adults. The obtained results showed significant decrease in adult emergence, fecundity and fertility. Chlorfluazuron caused also a significant prolongation in larval and pupal developmental period. When 4^th larval instar treated with LC₅₀ value of Chlorfluazuron (1.2ppm) female production and male's perception to pheromone affected. The results indicated that both treated and untreated sexes of the rust red flour beetle could secrete a pheromone that was able to stimulate the opposite sex as well as its own sex. Although production and responsiveness of pheromone in untreated groups were significantly higher than treated one. Females secreted a pheromone that stimulated males is sex pheromone. While the pheromone secreted by males is an aggregation pheromone. Production and responsiveness to pheromone in untreated virgin sexes was significantly higher than treated one at photophase and scotophase. The  maximum production and perception of pheromone in untreated sex were at 15.00 p.m. While a peak in treated one was at 13.00p.m.