Freeze-dried black raspberry powder is considered as a potential cancer chemopreventive agent. In this study, we fed AOM/DSS treated C57BL/6J mice with diet containing black raspberry anthocyanins for 12 weeks and this led to a reduction in colon carcinogenesis. These animals had consistently lower tumor multiplicity compared to AOM/DSS-treated mice not receiving BRB anthocyanins. In AOM/DSS-treated mice, the number of pathogenic bacteria, including Desulfovibriosp and Enterococcus spp, were increased significantly, whereas probiotics such as Eubacterium rectale, Faecalibacterium prausnitzii and Lactobacillus were dramatically decreased, but BRB anthocyanins supplement could reverse this imbalance in gut microbiota. BRB anthocyanins also caused the demethylation of the SFRP2 gene promoter, resulting in increased expression of SFRP2, both at the mRNA and protein levels. Furthermore, the expression levels of DNMT31 and DNMT3B, as well as of p-STAT3 were down-regulated by BRB anthocyanins in these animals. Taken together, these results suggested that BRB anthocyanins could modulate the composition of gut commensal microbiota and changes in inflammation and the methylation status of the SFRP2 gene may play a central role in the chemoprevention of colorectal cancer.