Nitromezuril (NZL) is a novel triazine compound that exhibits remarkable anticoccidial activity. However, mutagenicity and genotoxicity of NZL have not been evaluated to date. This study evaluated the potential risks of NZL by testing for bacterial reverse mutation (Ames), mouse sperm abnormality (SA), bone marrow micronucleus (MN) and chromosomal aberration (CA). Mice were orally administered with NZL at 385, 192 and 96mg/kg, corresponding to 0.5×, 0.25× and 0.125× the LD50 of NZL, respectively. No significant increases in SA and CA were found in mice treated with NZL for 5d and 3d, respectively (P >0.05). NZL at 96–385mg/kg did not have significant influence on micronucleated polychromatic erythrocyte counts (P >0.05). These results suggest that NZL is not genotoxic. However, Ames test results were positive both with and without the S9 system for Salmonella typhimurium TA98 and TA100, suggesting that NZL may be mutagenic. The mutagenic effects of NZL were different in in vitro and in vivo assays. Further studies should be conducted to confirm the safety of using and developing NZL as a novel anticoccidial drug.