The present study investigated the effects of photoperiod on the development of immature stages, oviposition periods and adult longevity of the granary weevil, Sitophilus granarius L. at constant temperature of 27±2C° and 70±5°% R.H. in the laboratory. Statistical analysis proved considerable effect of 16 and 24 hr. photophase on the incubation period of eggs. At complete darkness the shortest larval duration (19.6 days) was observed while the longest one (25.3 days) was shown at 24 hr. photophase. Pupal exposed to continuous light showed the lowest mean pupal period (4.7 days) as compared with 5.4 days for the pupal exposed to 16 hr. light. In addition, the period from egg to adult was markedly influenced by the tested photoperiods. The longest developmental period (40.9 days) was observed under continuous light while the shortest one was recorded at complete darkness. The oviposition periods of adult females decreased by increasing the photophase periods. Adult females kept in complete darkness recorded the longest oviposition period (89.4 days). Meanwhile, the shortest period (84.6 days) was reported for females lived under continuous light. Also, adults exposed to complete darkness lived longer than those lived under continuous illumination, however both sexes lived nearly equal periods at any tested photoperiodic regimes