Diabetes is a major risk factor for cardiovascular disease (CVD). Investigations have shown that diabetics have a two to four fold higher risk of developing CVD (Kannel et al.,1979). Tender coconut water (TCW) is rich in minerals (Potassium, calcium and magnesium),L-arginine,Vitamins (B and C) which are known to reduce the risk of developing Coronary Heart Disease (Anurag and Rajamohan 2003).TCW have been reported to have cardio-protective effect (Nnodim et. al.,2013). However, there are very few studies on its cardio-protective effect in diabetes. Therefore the aim of this study was to investigate the effects of Tender coconut water on the coronary artery of male diabetic Wistar rats. Twenty (20) male Wistar rats were selected for this study. The rats in each group were allowed access to feed and water ad libitum. All experiments were conducted in accordance with the National Institute of Health Guide for the Care and Use of Laboratory Animals. Diabetes mellitus was induced in rats by a single intraperitoneal injection of streptozotocin (STZ) (60mg/kg body weight) dissolved in 0.1M sodium citrate buffer (pH 4.5). Rats found to have blood glucose levels between ≥ 250 mg/dl were considered diabetic and randomly assigned into groups B, C and D. Diabetes was allowed to develop and stabilize in these STZ-treated rats over a period of 72 hours. Before the induction of diabetes, all the rats were fasted for 16-h (overnight), but still allowed free access to water throughout. At the end of the 16-h fasting period – taken as 0 time (i.e., 0h) – blood glucose levels (initial glycemia, G0) were determined and recorded. Rats in group A served as control; group B served as untreated diabetic group; diabetic rats in group C received 1IU/kg/day of Humulin subcutaneously and group D diabetic rats received 1ml/100g/day of TCW. The experimental period lasted for four weeks after initial glyceamia. The results obtained showed that there was a significant reduction (P<0.05) in the Fasting Blood glucose concentration of diabetic rats treated with Humulin and TCW compared with untreated diabetic rats. Histological studies of the heart of untreated diabetic rats showed coronary artery with focal intimal ulceration, lumen obstruction and hypertrophy of the muscular wall. The wall of the coronary artery of Diabetic rats treated with TCW and Humulin appear normal compared with the control. Histochemistry of elastin fibers showed that there was a strong positive stain for elastin in the wall of the coronary artery of rats in control and those of diabetic rats treated with Humulin and TCW respectively. The wall of the coronary artery of untreated diabetic rats appear negative to elastin stain. The coronary artery of Wistar rats induced with diabetic and treated with humulin and TCW showed normal vascular wall as compared with control. The results from this study indicate that Tender coconut water has both glucose lowering and cardio-protective properties in diabetic rats.