Aim: Several medications affect bone metabolism and the rate of tooth movement. The objective of the present study was to test the hypothesis that treatment with immunosuppressant tacrolimus (FK506) can interfere with bone turnover, decreasing the rate of tooth movement. Methods: Sixty male Wistar rats were divided into four groups of 15 animals each: Group 1: rats subjected to orthodontic movement plus treatment with saline solution vehicle; Group 2: rats subjected to orthodontic movement plus treatment with FK506; Group 3: rats treated with FK506 only; and Group 4: rats treated with saline solution vehicle only. The FK506 dose was 2 mg/kg/day. The treatment was initiated 14 days before the appliance installation and then kept for up to 14 days. In addition to the administration of the immunosuppressive drug, 10 mg/kg of oxytetracycline were injected at intervals of three days in order to show osteoblastic activity and bone growth at a histological level. Results: Histomorphometrical measurements showed greater tooth movement in Group 1 than in Group 2 at all periods (days 3, 7 and 14), though significant difference (p < 0.05) was observed only on days 7 and 14. Conclusions: FK506 significantly influenced the rate of tooth movement in rats subjected to the application of this medication.