This study aimed to reveal the effects of coumarin on Lens culinaris Medik. The germinated and ungerminated seed counts of the experimental groups were determined and the EC50 value was calculated by probit analysis. In biochemical studies, catalase and superoxide dismutase enzyme activities were investigated together with lipid peroxidation and hydrogen peroxide quantities. The results demonstrated an increase in the amount of malondialdehyde, a measure of lipid peroxidation, a decrease in the amount of H2O2 and EC50 value in the CAT activity and an increase in the EC50x2 value. In real-time PCR analysis, three different genetic expressions related to abiotic stress (CAT, Cu / Zn SOD and Mn SOD gene expression) were examined It was determined that coumarin caused genotoxic and biochemical damage on L. culinaris.