Carbosilane dendrimers containing vanillin on the surface have been prepared with the purpose of combining the unique antioxidant and anticancer properties of polyphenols and dendrimers. These new compounds exhibit antioxidant potency as free-radical scavengers, as determined by DPPH and ABTS. Remarkably, all synthesized dendrimers exhibit improved antioxidant efficacy compared to vanillin. Anticancer activity has been studied against HeLa cervical and PC3 human prostate cancer cell lines. Proliferation, cell cycle, adhesion and migration in human prostate tumor cells have been studied. Data revealed a general trend indicating that polyphenolic dendrimers are more cytotoxic than their monopolyphenolic counterparts in both cancer cell lines.