Germline HOXB13 G84E mutation has been consistently associated with prostate cancer (PCa) risk, but its association with other cancers is controversial. We systematically tested its association with the 20 most common cancer types in subjects from the UK Biobank. The G84E mutation was found in 1,545 (0.34%) of 460,224 participants of European ancestry. While mutation status did not associate with cancer risk in females, it was significantly associated with increased risk in males; odds ratio (OR) (95% confidence interval) for overall cancer diagnosis was 2.19 (1.89-2.52), P = 2.5E-19. The association remained after excluding PCa; OR = 1.4 (1.16-1.68), P = 0.003, suggesting association with other cancers. Indeed, suggestive novel associations were found for two other cancer types; rectosigmoid cancer, OR = 2.25 (1.05-4.15), P = 0.05 and non-melanoma skin cancer (NMSC), OR = 1.40 (1.12-1.74), P = 0.01. For NMSC, the association was found only in basal cell carcinoma, OR = 1.37 (1.07-1.74), P = 0.03. These findings have potential clinical utility for genetic counselling regarding HOXB13.