Abstract Purpose: To evaluate the efficacy of nivolumab and comparison with dacarbazine (DTIC) on peritoneal carcinomatosis of malignant melanoma in mouse model. Methods: Mouse skin melanoma cells was injected under the capsule of the peritoneal surface in the left side of the abdomen. On postoperative day ten, mouses randomised into three groups. Group 1: Control, Group 2: HIPEC (Hyperthermic intraperitoneal chemotherapy) with DTIC and Group 3: HIPEC with Nivolumab. After the sacrification on postoperative day fifteen, peritoneum evaluated macroscopically and histopathologically by using peritoneal regression grading score (PRGS). Results: In the 15th day exploration, all animals developed extensive intraperitoneal tumor growth in Group 1. In Group 2 and Group 3 median tumor size was 0.7±0.3cm and 0.3±0.2cm respectively (p: 0.023). Peritoneal carcinomatosis index (PCI) were significantly lower in Group 3 than other groups (p: 0.019). The lowest total tumor nodules in group 3 was 4 ± 2. The PGRS score was found significantly lower in Group 3 than other groups (p: 0.03). Lymphocytic response rate was found higher in the Group 3. Conclusions: It has been found that nivolumab significantly better than DTIC on peritoneal metastases of malign melanoma in mouse models. Nivolumab treatment gives promising results with pathological evidence in the treatment of metastatic disease of malignant melanoma.