The toxicity of some mosquito larvicides (Bacillus thuringiensis ssp. israelensis, spinosad, diflubenzuron and pyriproxyfen) on mosquito predator insect, backswimmer (Notonecta sp.) was investigated by exposing the predator to doses recommended by World Health Organization in laboratory conditions. At least ten nymphs (3rd and 4th in-stars) of backswimmers were released in polyethylene drums containing tap water treated with test doses by using a fish net. For testing each level of dose, four replicates were used and one control group was set up as negative (only tap water). The number of dead nymphs was counted in one day intervals for the 7 days exposure period, during which the nymphs were fed with non-larvicide-exposed mosquito larvae and pupae. According to the results, the four larvicides showed no or low toxic effect to Notonecta sp. nymphs in 7-day exposure time except for the highest doses of spinosad (500 g ai/ha, 68.75% mortality) and diflubenzuron (100 g ai/ha, 44.32% mortality).