A 71-year-old woman was admitted to the hospital on 7 July 2020 diagnosed with critically ill COVID-19 disease on a ventilator. The symptoms started three days before; fever, fatigue, and shortness of breath. She had a history of hypertension and diabetes mellitus. Blood test showed signs of severe inflammatory immune response and critical of clinical course. An intervention of Umbilical Cord Mesenchymal stem cells (UC-MSCs) therapy was planned as an add-on therapy. Evaluation was conducted by clinical presentation, blood drawing and radiography examination. We highlight that the patient showed promising clinical, laboratory, and radiological improvement after therapy. However, we cannot conclude whether the improvement is caused by UC-MSCs therapy itself since it is only a single case report and an old case report that the Covid-19 vaccinations are not already available at that time. Therefore, further studies were needed to investigate this result.