This study was designed to investigate the inhibitory effects of Polyopes lancifolia extract (PLE) on ${alpha}$-glucosidase activity, ${alpha}$-amylase activitiy, and postprandial hyperglycemia in streptozotocin (STZ)-induced diabetic mice. The results of this study revealed a marked inhibitory effect of PLE on ${alpha}$-glucosidase and ${alpha}$-amylase activities. The $IC_{50}s$ of PLE against ${alpha}$-glucosidase and ${alpha}$-amylase were 0.20 mg/mL and 0.35 mg/mL, respectively. PLE was a more effective inhibitor of ${alpha}$-glucosidase and ${alpha}$-amylase activities than acarbose, the positive control. The postprandial blood glucose levels of STZ-induced diabetic mice were significantly lower in the PLE treated group than in the control group. Moreover, PLE administration was associated with a decreased area under the curve for the glucose response in diabetic mice. These results indicate that PLE may be a potent inhibitor of ${alpha}$-glucosidase and ${alpha}$-amylase activities and may suppress postprandial hyperglycemia.