Herbs have been used as medicinal for several years to cure or rather manage different ailments such as diabetes mellitus. This is very common in rural settings of sub-saharan Africa and is now being adopted in urban areas. Opunta species have widely been seen to contain antihyperglycaemic effects. To evaluate the antihyperglycaemic and histopancreatic effect of aqueous extract of prickly pear cactus (Opuntia species) cladodes in streptozotocin-induced diabetic male Wistar rats in vivo. This was a laboratory based research conducted at Mulungushi University involving 30 wistar rats (Rattus norvegicus) that weighed between 160-200 g which were randomly selected into five groups (6 per cage); normal control, diabetic control, diabetic +metformin, diabetic +cactus and cactus only group. Initial blood glucose levels were obtained from the tail and record then Diabetes mellitus was induced using a single intraperitoneal dose of streptozotocin (70mg/kg BW) and established a persistent state of hyperglycemia after 72hours. The aqueous cactus extract of 100 mg/kg BW and metformin of 100 mg/kg BW was administered orally using intragastric cannula daily for a period of 4 weeks. At the end of the fourth week, Diabetes + cactus and diabetes + metformin groups body weights were statistically significant when compared to the diabetic group (P<0.05). While diabetic group was statistically significant when compared to normal control (P<0.05). The relative weight of the pancreas in diabetic group was statistically significant to other groups (P<0.05). The blood glucose in diabetic + cactus was normoglycaemic at 3rd week, Diabetic + metformin group when compared to diabetic group was statistically significant (P<0.05). The normal control and cactus only groups maintained normoglycaemic till the end of the 4th week. The histological findings of the normal control and cactus only group showed normal pancreatic cytoarchitecture. Diabetes group showed high degree of disorganization in the cytoarchitecture in the islet with reduction in β cell mass and deposition of elastic fibres. The Diabetic+Metformin group showed slight decrease in the cell mass (β cells) and elastic fibres were extensively deposited. Diabetic+Cactus treated group exhibited normal histology of the pancreas with increased number of β cells. Opuntia species are able to lower elevated blood glucose levels and ameliorate the effects of STZ on the pancreatic morphology