Epidermal keratinocytes overgrow in response to ultraviolet-B (UVB), which may be associated with skin photoaging and cancer development. Recently, we found that HIF-1Ձ controls the keratinocyte cell cycle and thereby contributes to epidermal homeostasis. A further study demonstrated that HIF-1Ձ is down-regulated by UVB and that this process is involved in UVB-induced skin hyperplasia. Therefore, we hypothesized that the forced expression of HIF-1Ձ in keratinocytes would prevent UVB-induced keratinocyte overgrowth. Among several agents known to induce HIF-1Ձ, pyrithione-zinc (Py-Zn) overcame the UVB suppression of HIF-1Ձ in cultured keratinocytes. Mechanistically, Py-Zn blocked the degradation of HIF-1Ձ protein in keratinocytes, while it did not affect the synthesis of HIF-1Ձ. Moreover, the p21 cell cycle inhibitor was down-regulated after UVB exposure, but was robustly induced by Py-Zn. In mice repeatedly irradiated with UVB, the epidermis became hyperplastic and HIF-1Ձ disappeared from nuclei of epidermal keratinocytes. However, a cream containing Py-Zn effectively prevented the skin thickening and up-regulated HIF-1Ձ to the normal level. These results suggest that Py-Zn is a potential agent to prevent UVB-induced photoaging and skin cancer development. This work also provides insight into a molecular target for treatment of UVB-induced skin diseases.