The studies on natural compounds to diabetes mellitus treatment have been increasing in recent years. Research suggests that natural components can inhibit alpha-glucosidase activities, an important strategy in the management of blood glucose levels. In this work, for the first time in the literature, the compounds produced by Ganoderma lipsiense extracts were identified and evaluated on the inhibitory effect of these on alpha-glucosidase activity. Four phenolic compounds were identified by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) to crude extract from G. lipsiense grown in red rice medium (RCE) and synthetic medium (SCE), being syringic acid identified in both extracts. Gas chromatography-mass spectrometry (GC-MS) analysis showed fatty acids and their derivatives, terpene, steroid, niacin, and nitrogen compounds to SCE , while RCE was rich in fatty acids and their derivatives. Both extracts demonstrated alpha-glucosidase inhibition ( RCE IC 50  = 0.269 ± 8.25 mg mL −1 ; SCE IC 50  = 0.218 ± 9.67 mg mL −1 ), and the purified hexane fraction of RCE ( RHEX ) demonstrated the highest inhibition of enzyme (81.1%). Studies on kinetic inhibition showed competitive inhibition mode to RCE , while SCE showed uncompetitive inhibition mode. Although the inhibitory effects of RCE and SCE were satisfactory, the present findings identified some unpublished compounds to G. lipsiense in the literature with important therapeutic properties.