The hypoglycemic effect of Solanum melongena peels extract (SMPE) on diabetic mice was investigated. LC-QTOF-MS was employed to clarify the material basis of SMPE. Different concentrations of SMPE, and the positive control, the drug acarbose, were used for in vitro experiments to conduct the α-glucosidase activity inhibition tests to determine the inhibition rate. In in vivo experiments, the diabetic mouse model was established through injecting alloxan intraperitoneally into mice, and the experimental mice were divided into 7 groups: the control group, normal administration group (normal mice were given 15 g/kg SMPE), SMPE high-dose group (SMPE 15 g/kg), SMPE medium-dose group (SMPE 5 g/kg), SMPE low-dose group (SMPE 2.5 g/kg), positive drug group (acarbose 1 g/kg), and model group. After continuous intragastric gavage for 4 weeks, the body weight, fasting blood glucose level, and glucose tolerance were measured. The results showed that the α-glucosidase inhibitory rate of 10 mg/mL SMPE was 49.13%, and SMPE at different concentrations inhibited α-glucosidase in a dose-dependent manner. SMPE had no effect on body weight and fasting blood glucose in normal mice. Compared with the model group, the body weights of the SMPE low-, medium-, and high-dose groups increased by 20.34%, 23.91%, and 15.20%, respectively, and the fasting blood glucose values decreased by 5.97%, 11.91%, and 42.20%, respectively. SMPE exhibited a significant hypoglycemic effect in diabetic mice, and the underlying mechanism may be related to the abilities of SMPE to inhibit the activity of α-glucosidase and delay the intestinal absorption of glucose.