The fruits of Gleditsia species (Fabaceae) have been known in traditional medicine as a saponin-rich herbal medicine. The present study aimed to investigate the effects of the total methanolic extract of Gleditsia caspica (MEGC) and its saponin-containing fractions (SFGC) on hyperglycemia in streptozotocin (STZ)-induced diabetic rats. A single intraperitoneal injection of STZ (55 mg/kg body weight) was used to induce hyperglycemia in male albino rats. MEGC (15, 30 and 60 mg/kg, p.o.) and SFGC (15, 30 and 60 mg/kg, p.o.) were administered to the diabetic rats daily for 14 days. The anti-diabetic drug gliclazide (10 mg/kg, p.o.) was used as a positive control. Blood samples were collected from overnight fasted rats for the evaluation of the antihyperglycemic, antihyperlipidemic and antioxidant activities. The levels of glucose, triglycerides (TG), cholesterol (TC) and malondialdehyde (MDA) were increased significantly, whereas the levels of α-amylase, insulin and reduced glutathione (GSH) were decreased in the experimental diabetic rats. Pancreas and liver of the diabetic rats exhibited significant changes in the histopathology, morphology and DNA content. Administration of MEGC or SFGC led to a decrease in the levels of glucose, TG, TC and MDA. In addition, the levels of α-amylase, insulin and GSH were increased in MEGC and SFGC treated diabetic rats. Also, the histopathological and morphological changes, as well the changes in DNA were significantly reversed by the extracts. Thus, MEGC and SFGC exhibited potent hypoglycemic and hypolipidemic activities in STZ- induced diabetic rats.