Cantharellus cibarius is one of the most important wild, edible, and ectomycorrhizal mushrooms growing at La Malinche National Park, Tlaxcala, Mexico; therefore, the assessment of its biological properties is of great interest to know its potential as an alternative treatment to chemopreventive strategies when it is consumed as part of a diet. Comet assay was used to evaluate the antigenotoxic properties of several concentrations of aqueous extracts (0.0125, 0.025, 0.05, 0.1, and 0.2% w/v) prepared at room temperature (22 ± 2°C). As a test system we used human mononuclear cells exposed to methyl methanesulphonate (MMS) in vitro according to 3 different protocols: previous, simultaneous, and posterior. Previous (0.0125%) and simultaneous (0.1%) treatments resulted in the highest inhibitory efficiency. In the former, the cells assessed showed a tail length of 94.9 ± 64 µm; in the latter, the tails measured 106.2 ± 40 µm. Resulting percentages of reduction in damage were 236% and 196.1%, respectively. We did not obtain a dose-dependent response. The mean tail length for each protocol (previous, 133.1 ± 80 µm; simultaneous, 127.8 ± 57 µm; posterior, 146.3 ± 74 µm) was statistically significant with regard to the positive control (MMS).