Knowledge about the effects of pesticides on biological control agents is required in order to successfully implement integrated pest management programs. The predatory mite Amblyseius swirskii Athias-Henriot has been used to control thrips, whiteflies, and broad mites in vegetable production; however, effects of fenpyroximate, an acaricide and insecticide used in vegetable crops, on A. swirskii have not been evaluated. The effect of four residual concentrations of fenpyroximate on A. swirskii females was measured under laboratory conditions including its effect on their fecundity and larval survival. Fresh residues of fenpyroximate were significantly toxic to adult females and larvae. Mortality increased and fecundity decreased as the concentration (0.026–0.208 ml/50 ml of water) and time after treatment (24–120 h) increased. Fifty percent of the larvae survived on the two lower concentrations (0.026 and 0.052 ml/50 ml of water) after 120 h.