Heating for disinfestation has been practiced of at the condition of 55-60°C for at least 48 hours in various facilities of stored and processed agricultural products. However, it has been required to reduce temperature and time due to the economic efficiency. To improve disinfestation efficiency of heating, we demonstrated whether combined treatments of heat with other agents exert synergistic for disinfestation. Heat treatments were combined with 1 ppm diatomaceous earth (DE), 10 ppm phosphine or 10% carbon dioxide against Plodia interpunctella, Sitophilus zeamais and Tribolium castaneum. Insects were treated single or multiple combinations of each component for 6 h at either 25°C or 40°C, then mortalities were monitored for 14 days post-treatments. Combined treatments greatly enhanced mortalities and shorten killing time of three species rather than single treatments. Particularly, heat treatments with 1 ppm DE and 10 ppm phosphine completely lethal within 3-6 h post-treatments, but heating with 10% CO2 was not much effective. Among three species, S. zeamais adults were more suscpetable to heat but both larvae and adults of T. castaneum was highly susceptible to phosphine. Our results clearly showed that combined treatment of DE or phosphine with mild heating (40°C) greatly improved mortalities of three major stored pest insects and provide advanced techniques for disinfestation of stored product pests.