Summary Background Chronic wound or nonhealing ulcer is essentially a wound that does not progress normally through the wound healing process. This study assessed the healing effect of umbilical cord Wharton's jelly stem cells seeded on biological scaffold in chronic skin ulcers. Materials and Methods In a randomized clinical trial, five patients between 30 and 60 years with chronic diabetic wounds were enrolled. To cover the wounds, acellular amniotic membrane seeded with Wharton's jelly mesenchymal stem cells (WJSCs) was used for 9 days, every 3 days with a follow‐up of 1 month. The percentage and time of wound healing and the size of wound were recorded for each patient. Results In treated patients, the wound healing time and wound size significantly decreased, and after 6 and 9 days, the wound size significantly declined ( P < 0.002). Conclusion As WJSCs seeded on amniotic membrane could significantly accelerate the healing effect in chronic diabetic wounds, they can be an alternative source in tissue engineering and repair of chronic ulcers.