Tetranychus urticae Koch and Tetranychus kanzawai Kishida are important pest mites of various crops of economic importance around the world. Prey consumption and functional responses of two species of phytoseiid mites on these two spider mites were evaluated at 25 ± 1°C, 65 ± 10% RH in the artificial climatic chamber with a photoperiod of 16 h light:8 h dark. The functional response of both Neoseiulus species was type II on three immature stages (egg, larva and protonymph) of Tetranychus species. The value of attack rate coefficients (α) of N. californicus to each stage of Tetranychus was greater than N. longispinosus, and the shortest handling time (T_h) was obtained on larvae followed by nymphs and eggs. The maximum attack rate (T/T_h) on eggs, larvae and nymphs of T. urticae was estimated to be 11.87, 37.23 and 26.95 for N. californicus, and 18.43, 28.98 and 20.67 for N. longispinosus; the maximum attack rate (T/T_f) on eggs, larvae and nymphs of T. kanzawai was estimated to be 11.90, 42.97 and 39.60 for N. californicus, and 24.15, 31.60 and 24.45 for N. longispinosus. When different densities of prey were offered to the predators, more prey was consumed at higher prey densities, and interaction between prey stage and prey density was significant for N. californicus, but not significant for N. longispinosus. The ability of N. californicus preying on larvae and nymphs of both Tetranychus species was significantly greater than N. longispinosus at high prey densities, but N. longispinosus consumed more eggs than N. californicus.