Diabetes is an important human ailment afflicting many from various walks of life in different countries. Since several years ago, medicinal plants are being looked up once again for the treatment of diabetes. In this sense, the objective of this study was to evaluate the hypoglycemic activity of Tabebuia rosea in a diabetic rat model. The ethanolic and chloroformic extracts of T. rosea crust were administered orally at different doses to diabetic rats. In addition, the glucose concentration was quantified every 24 h by one month before gastric administration of extracts. On the other hand, the hypoglycemic effect of T. rosea was compared with the activity induced by glibenclamide, metformine and lapachol. The results indicate that hypoglycemic activity exerted by the extracts (ethanolic and chloroformic) of T. rosea was in a dose-dependent manner and in a form similar with lapachol to a minimum dose (10 mg/kg) and different with both metformin and glibenclamide. These results suggest that responsible compound of hypoglycemic activity induced by T. rosea is lapachol. Key words: Tabebuia rosea, lapachone, metformine, glibenclamide.