Recently, numerous studies have attempted to search for new natural cosmeceuticals from marine resources. In this study, we focused on the protective effect of chitooligosaccharides (COS) with different molecular weight on cellular damage by ultraviolet mediated oxidative stress in human dermal fibroblast cells. Our results showed that the protective effect of COS on ultraviolet mediated dermal fibroblasts was dependent on their molecular weights. Additionally, expression of matrix metalloproteinases (MMPs) by ultraviolet ray might be result in aging process. COS suppressed ultraviolet mediated oxidative stress and DNA damage by generation of reactive oxygen species (ROS) in human dermal fibroblasts. Moreover, COS inhibited expression of MMPs including collagenases and gelatinases in the levels of mRNA and protein, respectively. Therefore, our results indicated that COS can be developed as anti-aging cosmeceuticals and their effects might be mediated via inhibition of MMPs expression and oxidative stress.