Stem cell-based therapies have recently opened up new horizons for treatment of various types of diseases including diabetes mellitus. However, long-term efficacy and safety of these novel modalities still remain a serious question. Hereby, we aim to report the one-year follow-up results in the diabetic patients who underwent fetal liver-derived hematopoietic stem cell allotransplantation. Fifty six patients with type one (n=30) and type two (n=26) diabetes, aged 10-58 years old (32.8 ± 16.3) were divided into the intervention and placebo group. The patients in the intervention group underwent fetal liver-derived hematopoietic stem cell transplantation while the patients in the placebo group received 5 ml of normal saline both via an intravenous route. The patients were visited at regular intervals to evaluate the efficacy of transplantation in glycemic control as well as possible complications. In the 6th month of the follow-up, there was a significant decrease in HbA1c levels in all groups without any rise in the fasting c-peptide. However, none of the precipitants transiently or continuously became insulin free in the first year after transplantation. It can be concluded that, in this study, fetal liver-derived hematopoietic stem cell transplantation had no significant effects on glycemic control. The heterogeneity of our patients might account for the negative results. Hence, longer follow-up results will be reported in the near future.