Experiments were conducted in the laboratory and the greenhouse to assess the effects of five acaricides against Tetranychus urticae Koch and its natural enemy Phytoseiulus persimilis Athias-Henriot. The acaricidal activity of the tested compounds against T. urticae was assessed by the slide dip and leaf disk dip techniques. Data showed that slide dip technique was efficient method to screen abamectin, chlorfenapyr and fenpyroximate; while the leaf disk dip technique was efficient method to determine the toxicity of ethion and etoxazole. The difference between the compounds may be due to their mode of actions. Results indicate that ethion, chlorfenapyr and etoxazole are very less toxic to P. persimilis adult females than those of T. urticae. Direct count for each of the prey and predator in order to assess the impact of compounds tested under greenhouse conditions, confirmed the results obtained to a large extent in the laboratory experiments.