Xanthohumol is a hop-derived flavonoid that has been widely examined for its health-protecting and antitumorigenic properties, but not yet in a natural beer matrix. The aim of the study was to investigate the antitumorigenic potential of a xanthohumol-enriched beer in vivo. Four groups of 4 × 10 nude mice were formed. Following the injection of HeLa tumorigenic cell lines, the treatment groups were administered a xanthohumol supplementation for 100 days, either dissolved in beer or in an ethanolic solution with the same alcohol strength as beer. The control groups received un-supplemented material. The terminal tumor masses, liver weights, and plasma antioxidant capacities (FRAP and ABTS methods) were measured. For the statistical analysis, a two-way ANOVA test was performed (p < 0.05). There were no statistically significant differences in tumor size between the groups. Xanthohumol did not induce higher levels of plasma antioxidant capacity, neither in beer nor in the water-ethanol matrix. The terminal liver weights were significantly higher in the control group receiving the unsupplemented ethanol solution. Xanthohumol dissolved in beer or in the water-alcohol matrix did not have a protective effect on tumor growth, nor did it have a positive effect on plasma antioxidant capacity either. However, beer with added xanthohumol had a less harmful effect on the liver compared to the supplemented water-ethanol solution. Our results indicate the possible negative countereffect of ethanol; however, further investigations are needed.