ABSTRACT : Along with the development of agriculture, chemical industries also entered a constant flow of increased quality and quantity of agricultural products through pesticides. Among these, Organophosphate Pesticides such as Chlorpyrifos are largely used in agriculture, especially in the cultivation of tomatoes. In this study, Chlorpyrifos residues were determined based on two treatment methods (immersion and spray), pesticide exposure time (1 and 10 minutes),and tomato washing method in the final product. Insecticide residues were quantified using thin layer chromatography. The results showed that the residue level in the samples immersed with pesticide for 10 min was higher than in both samples immersed for 1 min and in sprayed ones. No significant difference (P<0.05) was observed in pesticide residue at two time levels of pesticide application for the immersion method but the results have significantly different between spray and immersion techniques. In comparison to the other methods, spraying left the least amount of Chlorpyrifos residue in samples. Regarding tests to evaluate the effects of chlorinated wash water on Chlorpyrifos residue, there was an increase in pesticide residue levels in samples during this treatment.