Tap roots of Potentilla fulgens L. traditionally chewed along with betel nut (Areca catechu) and betel leaves (Piper betel), are commonly used by local practitioners for various types of ailments. The crude methanolic extract of the roots was tested for its effects in normoglycemic and alloxan-induced diabetic mice. Hypoglycemic activity was observed to be dose- and time- dependent. The extracts reduced blood glucose level 2 h following administration in both normal and alloxan-induced diabetic mice. In alloxan-induced diabetic mice blood glucose was markedly reduced by 63%, while in normal mice a 31% reduction was observed 24 h after the effective dose of extract was administered. Further, in the diabetic mice a prolonged anti-hyperglycemic action was observed where glucose levels was, found to be significantly low (79%) when compared with control even on the third day. Glucose tolerance was also improved in both normal and diabetic mice. The results were compared against those of insulin, glibenclamide, metformin, and the probable mechanism of action is discussed.