Phytoseiulus persimilis (Athias-Henriot) (Acari: Phytoseiidae), is known as a specialized predator of Tetranychus urticae (Koch 1836). In this study, laboratory bioassays were conducted to evaluate the effects of spiromesifen and spirodiclofen as tetronic acid derivatives on demographical characteristics of P.persimilis. The LC90 values obtained from the acute toxicity of each pesticide against T. urticae on P.persimilis population were determined with the leaf disc method under laboratory conditions (25 ± 2°C, 70 ± 5% relative humidity and 16:8 h (L:D)). Two acaricides tested significantly increased the total development time of both sexes of P.persimilis. The adults’ longevity, oviposition period, and mean fecundity decreased after exposure to treatments. The results indicated that adverse effects of the two treatments on population growth parameters (r, λ, R0, T) of P.persimilis were significant. The intrinsic rate of increase (r) in the control, and those treated with spiromesifen and spirodiclofen were 0.24, 0.18 and 0.12 days−1, respectively. For spiromesifen The net reproduction rate (R0), and finite rate of increase (λ) were reduced 1.66 and 1.07 fold in comparison to the control treatment, respectively. These measures for spirodiclofen were 3.45 and 1.12 in the same order. The intrinsic rate of increase (rm), net reproduction rate (R0), and finite rate of increase (λ) were significantly reduced in treated females compared to the control. Although, spiromesifen and spirodiclofen treatments revealed the species ability to survive, grow, develop, and reproduce successfully after the use of lethal dose but results indicated that lethal dose of two pesticides had significant negative effects on life table parameters of P.persimilis.These quantities should not be used in combination with P.persimilis in integrated pest management programs aimed at control of T. urticae.