AIM: To investigate the efficacy and the safety of umbilical cord derived mesenchymal stem cell (UC-MSC) implantation in patients with retinitis pigmentosa (RP). METHODS: This prospective, single-center, phase 3 clinical study enrolled 124 eyes of 82 RP patients. The patients received 5 million UC-MSCs to the suprachoroidal area with a surgical procedure. Patients were evaluated on the 1st day, 1st, and 6th months postoperatively. Best corrected visual acuity (BCVA), anterior segment and fundus examinations, color photography, optical coherence tomography (OCT), and visual ?eld (VF) tests were carried out at each visit. Fundus ?uorescein angiography (FFA) and multifocal electroretinography (mfERG) recordings were performed at the end of the 6th month. Ocular and systemic adverse events of the surgical procedure were also noted. RESULTS: All of the 82 patients completed the 6-month follow-up period. None of them had any serious systemic or ocular complications. There were statistically significant improvements in BCVA and VF during the study (all P<0.05). The amplitudes of the P1 waves in the central areas showed significant improvements in mfERG recordings. There were also significant increases in implicit times of P1 waves in the central areas. CONCLUSION: Suprachoroidal administration of UC-MSCs has beneficial effect on BCVA, VF, and mfERG measurements during the 6-month follow-up period. Cell mediated therapy based on the secretion of growth factors (GFs) seems to be an effective and safe option for degenerative retinal diseases.