Cruciferous vegetables, in particular those included into the Brassica genus, are good sources of a variety of nutrients and health-promoting phytochemicals. Phenolic compounds are the major antioxidants of Brassica; hence the contribution of Brassica vegetables to health improvement has largely been associated to their antioxidant capacity. This study aimed to assess anti-diabetic, antilipidemic, and antioxidant activity of phenolic rich extract of Brassica oleraceae var gongylodes (BOvG) in Wistar rats. The findings revealed that the administration of BOvG extract to diabetic rats significantly reduced fasting blood glucose by 64% within 7 days of treatment. Additionally, BOvG extract was also observed to normalize the diabetic rats' lipid profile and HbA1c (Glycated hemoglobin). BOvG extract also showed protection of liver- kidney functions, which was evidenced by the significant decrease in Blood Urea Nitrogen (BUN), Serum glutamic oxaloacetic transaminase (SGOT) and Serum glutamic pyruvic transaminase (SGPT). The treatment also improved the antioxidant status of the diabetic rats where the enzymatic activities of Catalase (CAT) and Super Oxide Dismutase (SOD) were significantly increased. Furthermore, RP-HPLC analysis detected chlorogenic acid, rutin, and sinapic acid against known standards in BOvG extract. Hence, the present investigation suggests that BOvG phenolic rich extract (as a multi-component therapy) exhibited anti-diabetic, antilipidemic and antioxidant properties in STZ-induced diabetic rats.