Abstract: Organ fibrosis is characterized by excessive deposition of extracellular matrix (ECMs), and is an intermediate pathological process of chronic organ disease developing into cancer. At present, there is still no effective anti-fibrosis strategy. As pluripotent stem cells, mesenchymal stem cells (MSCs) can promote the repair of fibrotic tissues by differentiation, immune regulation, paracrine and homing; besides, their exosomes (MSC-Exos) as the delivery vectors show great potential in the treatment of organ fibrosis by transferring their active components to injured cells or targeting recipient cells, providing a new option for the treatment of organ fibrosis. Based on liver fibrosis, lung fibrosis, kidney fibrosis, cardiac fibrosis, skin fibrosis and pancreatic fibrosis, this paper summarizes the mechanisms and applications of MSCs and MSC-Exos in the treatment of organ fibrosis, in the hope of providing new insights to further develop stem-cell therapy for fibrosis.