Aedes aegypti L. and Culex pipiens L. are among the world’s most common and medically important mosquitoes (Diptera: Culicidae). Each year, millions of people are infected with pathogens transmitted by these mosquitoes and thousands of people die from mosquito-borne diseases. Although chemical insecticides are widely used for vector control, most of them are highly toxic to the environment and human health. The harmful effects of chemical pesticides have led scientists to search for the less toxic, natural, and eco-friendly products. In this regard, lichens, a symbiotic association, are one of the organisms studied in the search for new insecticidal active substances. In this research, the toxicity of acetone, ethanol and methanol extracts from oakmoss lichen, Evernia prunastri (L.) Ach., a widely available epiphytic macro-lichen species, was investigated in of Ae. aegypti and Cx. pipiens. The extracts showed varying levels of toxic effect on the two mosquito species depending on the concentration and it is clear that methanol and ethanol extracts of E. prunastri were more toxic than the acetone extract according to the LC50 values. The LC50 values of methanol, ethanol and acetone extracts for Cx. pipiens older instar (third–fourth) larvae at 48 h were 104.3, 153.9 and 490.0 ppm, for young instars (first–second), they were 203.4, 326.6 and 606.9 ppm, respectively. The LC50 values of methanol, ethanol and acetone extracts for 48 h on Ae. aegypti young instar larvae were 390.9, 440.0 and 2934.8 ppm, and 537.1, 515.3 and 1837.1 ppm for older instar larvae, respectively. The highest contents of total flavonoids and phenolic compounds were determined in acetone extract of E. prunastri. The phenolic compounds in extracts range from 7.48 to 10.28 mg gallic acid/g and the flavonoid content of extracts range from 37.68 to 91.76 mg catechin/g. This is the first study on the toxic effect of E. prunastri extracts on mosquitoes and indicates that lichen extracts can be a source for developing environmentally friendly larvicides. Keywords: Aedes aegypti · Culex pipiens · Extract · Larvicidal · Mosquito · Oakmoss Lichen.