Eotetranychus hirsti Pritchard & Baker (Tetranychidae) is one of the important pests of fig trees that is widely distributed in fig orchards of Iran. The predatory mite Phytoseius plumifer Canestrini & Fanzago is a phytoseiid mite on fig that can feed and reproduce on E. hirsti. The effect of four constant temperatures (20, 25, 30 and 35°C) on demographic parameters of P. plumifer fed on nymphal stages of E. hirsti was determined under laboratory conditions at 50 ± 5% RH and a photoperiod of 16:8 h (L: D). The total developmental time of immature stages of this predator decreased with increasing temperature from 20°C to 35°C, and varied from 17.13±0.23 to 6.55±0.19 days for females. The lower temperature threshold (T_min) and thermal constant (K) for the total immature stages of this predator was estimated 10.33°C and 166.67 degree-days by the ordinary linear model, 11.17°C and 147.87 degree-days by the Ikemoto linear model, respectively. Female longevity was 67.79, 47.00, 35.11, and 27.42 days at 20, 25, 30 and 35°C, respectively. The highest values of total fecundity and daily fecundity were obtained at 25°C (35.71±1.73 eggs) and 30°C (1.57±0.02 eggs), respectively. The value of the intrinsic rate of increase (r_m) increased as increasing temperature from 20°C (0.064±0.0012 day^-1) to 30°C (0.180±0.0023 day^-1), and then decreased at 35°C (0.153±0.0037 day^-1). The highest and lowest values of the mean generation time (T) were 32.75±0.95 and 14.18±0.51 days, which were obtained at 20°C and 35°C, respectively. The results of this study revealed that of P. plumifer is effective predator of the fig spider mite and develops effectively at a broad range of temperatures.