Effects of sublethal exposure to abamectin on the biological performance of Neoseiulus longispinosus (Evans) were studied under ambient laboratory conditions of 28 ± 2°C and 80 ± 15% RH with 24 h light. The red form of the twospotted spider mite, Tetranychus urticae Koch, complex (Acari: Tetranychidae), was offered as prey. The LC₅₀ obtained from the contact bioassay at 48 h after treatment was 0.015 ppm (AI). A big change in kill for a given variation in dosage for the regression slope probably indicated that abamectin was unlikely selective. Sublethal exposures to abamectin caused a reduction in survival with the female reaching 50% mortality by the sixth day and the male 4 d later. The mean preoviposition period was extended by almost 1 d, whereas the mean oviposition period was shortened by almost 5 d causing a reduction in the mean fecundity female⁻¹ to almost half that of the untreated females. The net reproductive rate (R_o), the intrinsic rate of increase (r_m), and the finite rate of increase (λ) of the treated females were markedly inferior. Treated males were seriously affected; the mean life span was almost half that of the untreated.