We evaluated the possible protective effect of the popular Indian cruciferous vegetable mustard leaf (Brassica campestris) against chromosomal damage and oxidative stress induced by γ-radiation, cyclophosphamide (CPH) and urethane (URE), in mice. In vivo bone marrow micronucleus test was performed to assess chromosomal damage, and oxidative stress was monitored by estimating the changes in lipid peroxidation and the status of glutathione (GSH) as well as redox cycle antioxidants. Pretreatment with 50-250 mg/kg body wt of mustard leaf extract (MLE) for seven days significantly reduced the frequencies of micronuclei induced by γ-radiation, CPH and URE. The protective effect against chromosomal damage was associated with modulation of lipid peroxidation as well as an increase in GSH and the GSH-dependent enzyme glutathione S-transferase (GST). Mass spectral analysis showed the presence of glucosinolates in MLE used for the pretreatment of mice. These findings indicate that intake of the green leafy cruciferous vegetable mustard leaf can lead to protection against in vivo genotoxicity and oxidative stress.