The Red Flour Beetle, Tribolium castaneum (Herbst), is a key pest of stored products all over the world. The damages caused may result in reduced product quality and marketability. The use of insecticides and fumigants for the control of this pest has caused serious environmental problems and health hazards. Biologically based methods such as the use of botanicals and other means like the irradiation of insects, are gaining increasing role in the control of various storage pests. The aim of the present study was to determine the effects of gamma-irradiation on the mortality and protein content of Tribolium castaneum (Herbst). Doses ranging from 0.1kGy to 0.35kGy were applied. The mortality rates were higher in the irradiated insects than the control. The insect samples irradiated with 0.35kGy died within 6 Days after irradiation (DAI), while the samples irradiated with 0.1kGy died within 18 DAI. The protein content (estimated by Lowry’s Method) was much also reduced in the irradiated insects than the unirradiated ones. These results are encouraging and indicate that irradiation is an effective measure in the control of T.castaneum.