The ethanolic extract of Allium sativum, Mangifera indica and Vinca rosea formulations were experimented for its anti-diabetic and anti-obese properties in Streptozotocin induced diabetic male Wistar rats. The ethanolic extract of 50mg/kg, p.o. as a single dose used as treatment to the diabetic rats for a period of 24 days. The body weight was assessed for a time interval of 4 weeks. The body weight was found to be improved in the treatment group with an increase in changes compared to control and STZ induced diabetic group. This result proved the efficiency of plant extracts formulation as an anti-obese drug. The experimental rats subjected to OGTT showed decreased glucose levels in the plant extract treated group compared to the control and diabetic rats. From the above results, it is concluded that the plant extract formulation possesses significant anti-diabetic and anti-adipogenicity effects in STZ- induced diabetic rats.