Abstract Scar formation is an intractable medical problem that appears after skin wounds have healed. Recent research has shown that exosomes secreted by human adipose mesenchymal stem cells (ASC-Exos) can benefit wound healing. To further explore the therapeutic potential of ASC-Exos, we investigated their effects on mitigating scar formation, and the underlying mechanisms of these effects. We found that intravenous injection of ASC-Exos decreased the size of scars and increased the ratio of collagen III to collagen I in murine incisional wounds. Exosome treatment also prevented the differentiation of fibroblasts into myofibroblasts and increased the ratio of transforming growth factor-β3 (TGF-β3) to TGF-β1 in vivo. Additionally, we found that ASC-Exos increased the matrix metalloproteinases-3 (MMP3) expression of skin dermal fibroblasts by activating the ERK/MAPK pathway, leading to a high ratio of MMP3 to tissue inhibitor of matrix metalloproteinases-1 (TIMP1), which is also beneficial for the remodelling of extracellular matrix (ECM). In conclusion, our results demonstrated that ASC-Exos promote ECM reconstruction in cutaneous wound repair by regulating the ratios of collagen type III: type I, TGF-β3:TGF-β1 and MMP3:TIMP1, and by regulating fibroblast differentiation to mitigate scar formation. Therefore, the application of ASC-Exos may be a novel therapeutic approach for scarless wound repair.