Diabetes Mellitus (DM) has an estimated world prevalence of 285 million adults with high morbidity and mortality rates especially in the developing countries. The preparations of the seeds of Buchholzia coriacea commonly known as wonder kola is used for the management of DM in Nigerian ethnomedicine. In view of this, we studied the antidiabetic effects of the methanol extract of the seeds to scientifically ascertain the folkloric use. Alloxan induced diabetic rats were used in the study. Determination of the blood glucose concentration was done using the One Touch Ultra mini glucometer. Also acute toxicity test was performed using the Lorke’s method. Result showed an oral median lethality dose (LD50) greater than 5000 mg/kg, an indication of high safety profile. The extract at 100, 200, 400 mg/kg doses exhibited percentage blood glucose reduction (PBGR) of 37.73, 12.30 and 11.30 % respectively after 4 hours treatment. The combination of extract (100 mg/kg) and metformin (100 mg/kg) gave a PBGR at 4th and 7th day treatment of 73.4 and 72.2 % respectively. Therefore, the extract of the seeds of B. coriacea has potential hypoglycaemic effects and exhibited synergistic actions with metformin, a standard oral hypoglycaemic agent.