The antidiabetic and antioxidant activities of the ethyl acetate-soluble extract (MFE) of mulberry fruit (Morus alba L.) were investigated. In vitro, MFE showed potent α-glucosidase inhibitory activity and radical-scavenging activities against DPPH and superoxide anion radicals. In vivo, MFE could significantly decrease fasting blood glucose (FBG) and glycosylated serum protein (GSP), and increase antioxidant enzymatic activities (SOD, CAT, GSH-Px) in streptozotocin (STZ)-induced diabetic mice. Bioactivity-guided fractionation of the MFE led to the isolation of 25 phenolic compounds, and their structures were identified on the basis of MS and NMR data. All the 25 compounds were isolated from mulberry fruit for the first time. Also, the α-glucosidase inhibitory activity and antioxidant activity of the phenolics were evaluated. Potent α-glucosidase inhibitory and radical-scavenging activities of these phenolics suggested that they may be partially responsible for the antidiabetic and antioxidant activities of mulberry fruit.