UVB reduces type I procollagen levels and increases matrix metalloproteinases-1 (MMP-1) levels in human skin and plays a major role in the process of photoaging. We previously reported that fucoidan inhibits UVB-induced MMP-1 expression at the protein and mRNA levels in human skin fibroblasts (HS68). Yet, the effects of fucoidan on UVB-induced MMP-1 promoter activity and type I procollagen have not been investigated. In this study, we assessed the effects of fucoidan on the inhibition of MMP-1 promoter activity and on the increase of type I procollagen synthesis in human skin fibroblasts. Fucoidan treatment significantly inhibited MMP-1 promoter activity compared to UVB irradiation alone. Fucoidan treatment also increased type I procollagen mRNA and protein expression in a dose-dependent manner compared to the control. Our data indicate that fucoidan may prevent UVB-induced MMP-1 expression and inhibit down-regulation of type I procollagen synthesis. We suggest that fucoidan may be a potential therapeutic agent to prevent and treat skin photoaging.