Background The main objective was to evaluate the possible protective effect of Chuquiraga spinosa extract on N-methyl nitrosourea (NMU)-induced prostate cancer in rats and DU-145 cell line. Materials and methods Prostate carcinogenesis was induced in 30 male Holtzman rats by providing cyproterone acetate, testosterone, and NMU. The tumors were monitored and hematological and biochemical parameters and frequency of micronucleated polychromatic erythrocytes were recorded. The cell line was assessed by a cytotoxicity assay. Results Oral administration of C. spinosa extract significantly lowered superoxide dismutase malondialdehyde, NO, C-reactive protein, and prostate-specific antigen levels (all P < 0.01 compared with Inductor Group). There was a significant decrease in the frequency of micronucleated polychromatic erythrocytes (P < 0.05). C. spinosa presented a selectivity index of 17.24 in the cytotoxicity assay. Conclusions Considering its anti-inflammatory, antioxidant, and antigenotoxic effects, and important variations on biochemical and hematological parameters, including prostate-specific antigen of C. spinosa extract, we conclude that it has a protective effect on NMU-induced prostate cancer in rats and cytotoxicity in the DU-145 cell line.