Ellagitannins are well-known antioxidants in medicinal plants, foods, and edible fruits, particularly in Myrciaria cauliflora (jabuticaba). Thus, this study aimed to evaluate the protective effects of jabuticaba seed extract (JSE) and pedunculagin using in vivo micronucleus test and comet assay in mouse bone marrow cells, in combination with cyclophosphamide (CP), a bioreductive alkylating agent. The ellagitannin composition of JSE was determined by HPLC/PDA, with castalagin, vescalagin, and pedunculagin as the main compounds (124.4, 45.5, and 15.6mg/g dw, respectively). Results from pre- and co- treatments with JSE or pedunculagin clearly showed their protective action against CP-induced micronuclei and DNA damage. The effects of both tannins in post-treatments with CP suggested they influence DNA repair systems. These findings indicate that JSE and pedunculagin possess chemopreventive as well as DNA repair-inducing properties.