Schizotetranychus smirnovi Wainstein is an important phytophagous pest of almond trees which causes serious damage in southwestern Iran. Scolothrips longicornis Priesner has been considered as an efficient predatory thrips that feeds on this spider mite and hence its efficiency for controlling S. smirnovi should be evaluated. In the current study, all main biological parameters of S. longicornis fed on S. smirnovi were determined under laboratory conditions. Data analysis was performed using both female age-specific and age-stage, two-sex life table theories. Duration of incubation, larval, pre-pupal, pupal and pre-adult periods of male predators were 4.73, 3.18, 1.05, 1.86 and 10.82 days, respectively. These periods in female individuals lasted 4.57, 3.92, 1.04, 1.87 and 11.00 days, respectively. Our findings showed that each female laid an average of 62.74 eggs during its ovipositional period (13.61 days). Using the age-stage, two-sex life table, the values of the net reproductive rate (R₀), intrinsic rate of increase (r), finite rate of increase (λ) and mean generation time (T) were estimated to be 26.236 (eggs/individual), 0.171 (day^-1), 1.186 (day^-1) and 19.130 (days), respectively. Using the female age-specific life table, these parameters had different values. Our findings revealed that S. longicornis has a reliable capability to increase its population by feeding on S. smirnovi. This information can expand our knowledge for assessing biological efficiency of this predatory thrips in sustainable management of the destructive mite pest.