Susceptibility to photoimmune suppression and photocarcinogenesis is greater in male than in female humans and mice and is exacerbated in female estrogen receptor-beta knockout (ER-β-/-) mice. We previously reported that the active vitamin D hormone, 1,25-dihydroxyvitamin D3 (1,25(OH)2D) applied topically protects against ultraviolet radiation (UV)-induction of cutaneous cyclobutane pyrimidine dimers (CPDs) and suppression of contact hypersensitivity (CHS) in female mice. Here we compare these responses in female versus male Skh:hr1 mice, in ER-β-/- versus wild type C57BL/6 mice, and in female ER-blockaded Skh:hr1 mice. Induction of CPDs was significantly greater in male than female Skh:hr1 mice and was more effectively reduced by 1,25(OH)2D in female Skh:hr1 and C57BL/6 mice, than in male Skh:hr1 or ER-β-/- mice respectively. This correlated with reduced sunburn inflammation by 1,25(OH)2D in female but not male Skh:hr1 mice. Furthermore, although 1,25(OH)2D alone dose-dependently suppressed basal CHS responses in male Skh:hr1 and ER-β-/- mice, UV-induced immunosuppression was universally observed. In female Skh:hr1 and C57BL/6 mice, the immunosuppression was decreased by 1,25(OH)2D dose-dependently, but not in male Skh:hr1, ER-β-/- or ER-blockaded mice. These results reveal a sex bias in genetic, inflammatory and immune photoprotection by 1,25(OH)2D favoring female mice, that is dependent on the presence of ER-β.