Recently, much attention has been given to chitosan and its hydrolyzed products due to their diverse biological activities. For the first time here we report the inhibitory effect of chitooligosaccharides (COS) on activation and expression of matrix metalloproteinase-2 (MMP-2) in primary human dermal fibroblasts (HDFs). COS with 3-5 kDa exhibited the highest inhibitory effect on MMP-2 activity in HDFs assessed by gelatin zymography. Interestingly, protein expression of MMP-2 was also inhibited by COS with same molecular weight. This inhibition was caused by the decrease of the gene expression and transcriptional activity of MMP-2. Furthermore, it was found that COS repressed the gene expression of c-fos, a part of AP-1 transcription factor. These results suggest that COS may play an important role in the prevention and treatment of MMP-2 mediated several health problems such as metastasis and wrinkle formation.