This study investigates the genotoxicity of the essential oils extracted from the aerial parts of catmint (Nepeta meyeri Benth.) against two weeds (Bromus danthoniae and Lactuca serriola) and two crop plants (Brassica napus and Zea mays). The essential oils of N. meyeri analyzed by gas chromatography-mass spectrometry contained 14 compounds, with 4a, 7, 7a-nepetalactone (83.4%), 4a, 7, and 7a-nepetalactone (8.83%) as the major components. The oils were diluted (25, 50, 100, and 150ppm) and the solutions were applied to seeds or leaves of these plants. The study compared the germination percentage and random amplified polymorphic DNA (RAPD) results with the control group. The results showed that the oils had a strong inhibitory activity and caused a change in RAPD profiles in terms of variation in band intensity, loss of bands, and appearance of new bands compared with the control group. The results suggested that RAPD analysis could be applied as a suitable biomarker assay for the detection of genotoxic effects of plant allelochemicals. This study indicates the genotoxical potential of N. meyeri essential oils on weed and crop plants.