The polysaccharide (PPB-2) was extracted and purified from the fruiting body of artificially cultivated Phellinus baumii by an acid-chlorite delignification method. The in vitro hypoglycemic and in vivo hepatoprotective activities of PPB-2 were investigated. FT-IR spectra, NMR spectral analysis, and scanning electron microscopy were used to investigate the structural characterization of PPB-2. PPB-2 exhibited higher α-glucosidase and α-amylase inhibitory activities and showed significant inhibitory effects against the diffusion of glucose. Furthermore, the administration of PPB-2 to mice significantly prevented the increase of serum alanine aminotransferase and aspartate aminotransferase activities, as well as the increase in total cholesterol, triglycerides, and total bilirubin, and hepatic malondialdehyde levels, and PPB-2 enhanced the activities of superoxide dismutase and catalase, as well as the glutathione levels. The results suggest that PPB-2 may be suitable as a functional food with hypoglycemic and hepatoprotective activities.