Procyanidins are reported to inhibit α-glucosidase, which may be a useful attribute for developing functional foods that control post-prandial blood sugar levels. At present, the nature of the molecular interaction between procyanidins and α-glucosidase is poorly understood. In this study, spectroscopic analyses and computer simulations were used to investigate the interactions between α-glucosidase and B-type procyanidin dimer (BPD). Our results suggest that BPD binds to α-glucosidase through a combination of hydrophobic and hydrophilic interactions. This hypothesis was based on measurements of the intrinsic fluorescence quenching, conformational changes, and surface hydrophobicity of the α-glucosidase after binding. Thermodynamic analysis suggested that α-glucosidase had one binding site for BPD and that the interaction was spontaneous. Homologous modeling of α-glucosidase was used to provide information about the precise nature of the molecular interactions. Molecular docking analysis suggested that BPD formed hydrogen bonds and hydrophobic interactions with α-glucosidase when it bound to its active site. This research offers new insights into the mechanism of interaction between procyanidins and α-glucosidase, which may be useful for the development of functional foods to tackle type 2 diabetes.