Environmental factors, such as photoperiod can play an important role in the development and performance of predatory mites. The influence of five photoperiod regimes (0: 24, 8: 16, 12: 12, 16: 8, and 24: 0h; Light: Dark) on the population parameters of the predatory mites, Amblyseius swirskii Athias-Henriot and Neoseiulus cucumeris (Oudemans) was studied under the laboratory conditions at 25°C and 25 ± 1°C, 65 ± 5% RH. Regarding A. swirskii, the longest and shortest total pre-adult and total preoviposition periods (TPOP) were in the photoperiod of 12L:12D and 16L:8D, respectively. The oviposition days, adult longevity, total life span, fecundity, gross reproductive rate (GRR), and net reproductive rate (R0) of the predator had no significant difference in all photoperiods tested. The intrinsic rate of increase (r) and the finite rate of increase (λ) in 16L:8D photoperiod had no significant difference with the other photoperiods tested except 12L:12D. Regarding N. cucumeris, the shortest total pre-adult and TPOP were in full darkness. The oviposition days and fecundity were significantly higher in 16L:8D than the others. The value of R0 in 16L:8D was significantly higher than 8L:16D. The highest values of the parameters r and λ were observed in full darkness, which had no significant difference with 16L:8D and 24L:0D. According to the results, the photoperiod regime had a more significant influence in terms of development and reproduction on N. cucumeris than A. swirskii, and 16:8 (L: D) h photoperiod was recognized as the proper regime for their rearing.