Antidiabetic effects of ethanolic extract of Pleurotus ostreatus (mushroom) on alloxan-induced diabetic ratswas studied. The median lethal dose (LD50) of the extract was determined to be 3,472.14 mgkg-1 and a singledose of 380.0, 760.0 and 1140.0 body weight of the extract were intraperitoneally administered as thetreatment dose and the blood glucose levels (BGL) examined for 7 hours and 15 hours (prolonged) at 2 and 4hours intervals respectively. The extract exhibited significant (p<0.05 and p<0.01) reduction in the bloodglucose levels of the albino rats. The extract compared favourably with the standard reference drug(metformin) which all gave their maximum BGL reduction at 5 hours duration. The confirmation ofantidiabetic potentials of the Pleurotus ostreatus tuber has been justified in this study as claimed bytraditional medicine practitionersin Akwa Ibom State.