Aim: The purpose of this study was to determine the effect of mesenchymal stem cell (MSC) transplantation on the peritoneal morphology and inflammation markers in rat models of peritoneal dialysis (PD). Materials and methods: Wistar albino rats were divided into two groups: control (C) (n = 8) and experimental groups (n = 50). PD solution was given to the experimental group during 6 weeks. Then, experimental group was divided into three groups as PD, MSC, and placebo (P) groups. MSC group was treated with MSC (1.5 x 10(6) cells/kg) and P group was treated with phosphate buffer solution via intraperitoneal injection. Evaluation was performed to C and PD groups at the end of 6 weeks and to MSC and P groups at second and third week of the treatment (MSC-2, P-2, MSC-3, and P-3 groups). Results: The submesothelial area was significantly thickened in PD and P groups compared to C and MSC groups. Peritoneal fibrosis was seen in P-3 group but not in MSC group. There were no significant differences between the MSC-3 and C groups according to morphological findings. Levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were significantly increased in MSC-2 group compared to the other groups (p-values ranged from 0.0001 to 0.04). TNF-alpha and IL-6 levels in MSC-3 and P-3 groups were lower than PD and C groups (p < 0.0001 for TNF-alpha and p = 0.0001-0.002 for IL-6). Conclusion: Giving MSC may protect the peritoneal membrane from the deleterious effect of PD and extend the life of the peritoneal membrane. Our study is the first on this issue and more detailed studies are needed.