Spiromesifen is a widely used pesticide (acaricide) for controlling the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) which is a severe pest on strawberries in Mersin region of Turkey. The experiment was carried out, under laboratory conditions (25 ± 1 °C, 60 ± 10% relative humidity and 16-h light) for the evaluation of responses of the spider mite against spiromesifen. The responses (mortality rate, sensitivity) of mite populations to pesticide were estimated by calculation of the mortality rate or effectiveness ratio (% Abbott), for three different concentrations (recommended, 1/2 and 1/4 of applied rate). According to effectiveness ratio, the mite species shows oversensitivity to eggs and immature stages for spiromesifen which were classified as harmful. Adults of T. urticae were found less susceptible to this acaricide. Spiromesifen was considered to be the most toxic to the eggs. Eggs hatching ratio has been reduced by almost 90–100% at the recommended and other applied concentra-tions at 36–72 h (0.5, 0.25 and 0.125 μL/mL). Spiromesifen was found to be highly toxic on eggs hatching ratio at 48 hours. The highest effectiveness ratios estimated for immature stages were 79, 89 and 98% for each concentration respectively (0.5, 0.25 and 0.125 μL/mL). Given the adult stage of the two-spotted spider mite, the highest response was carried out at the recommended concentration, which has the mortality rate reaching over 96 % after 60 hours.