Abstract: Because of no previous study on the biology of the predatory mite Agistemus exsertus Gonzalez, as a biological control agent of two- spotted spider mite in Saudi Arabia, the effect of temperatures on A. exsertus was studied in laboratory. Predator and prey mite individuals were collected from egg plant leaves growing in a private farm at Hail province in 2010. Immature stages and adult predatory mites were divided into four groups and subjected to 20, 25, 30 and 35°C with 70% RH. Predatory mites were provided with immature stages of TSSM as a prey during their whole life span. Results showed that rising temperature shortened the incubation period of eggs and accelerated the development of A. exsertus. The highest rate of prey consumption of immature stages was obtained at 25°C and followed by 30, 35 and 20°C. Most of the prey consumption during longevity was obtained in oviposition period. In oviposition period, adult female consumed an average of 90.15, 82.28, 87.01 and 68.72% from the total number of prey individuals during female longevity when predatory mites were kept at 20, 25, 30 and 35°C, respectively. The temperature adversely affected life table parameters, where mean generation time (T) averaged 26.05, 27.23 and 28.46 days when mites were kept at 35, 30 and 25°C, while T increased to 36.66 days at 20°C, respectively. The highest value of net reproductive rate Ro was obtained at 30°C. Temperature also affected the intrinsic rate of increase rm of A. exsertus where it averaged 0.08, 0.11, 0.13 and 0.10 at 20, 25, 30 and 35°C, respectively. Rearing A. exsertus individuals at 25 and 30°C gave the best biological aspects represented by short development, high prey consumption and large number of deposited eggs and therefore, A. exsertus can be considered as a promising biological control agent against tetranychid mites in Hail, Saudi Arabia.