With the increasing prevalence of hypertension and diabetes mellitus in areas with high prevalence of HIV/AIDS, it is important to understand the co-existence of the conditions. More importantly, understanding the risk factors for improved prevention and clinical practice. A cross-sectional survey was conducted among 240 hypertensive patients with co-morbidities such as diabetes mellitus and HIV/ AIDS in Homa Bay County, western Kenya. Data was collected using a structured questionnaire and multiple regressions were used to identify the risk of diabetes mellitus controlling for age, smoking and HIV/AIDS infection. The study shows co-existing co-morbidities with 50% suffering from HIV/AIDS and another 50% from Diabetes mellitus among the hypertensive patients. In addition, the risk for diabetes mellitus were; smoking (COR=2.89, 95%CI=1.63-5.11, P<0.001) and HIV/AIDS (COR=2.40, 95%CI=1.40-4.08, P=0.001). Also, observed that between 45 and 75 years, the risk of diabetes increased two-fold and when we controlled for age and smoking, the risk of diabetes among the hypertensive patients with HIV/AIDS increased by 1.4 folds (AOR=3.30, 95% CI=1.79-6.05,P<0.001). The study shows high co-existence of hypertension, HIV/AIDS and diabetes mellitus. Further, shows age, smoking and HIV/AIDS as the risk factors for diabetes in the population. The findings underscore the need for improved health promotion on the risk of age and smoking and clinical practice for the co-existing health conditions.