It has been well documented that there is an increased prevalence of standard cardiovascular (CV) risk factors in association with diabetes and with diabetes-related abnormalities. Hyperglycemia, in particular, also plays an important role. Heart failure (HF) has become a frequent manifestation of cardiovascular disease (CVD) among individuals with diabetes mellitus. Epidemiological studies suggest that the effect of hyperglycemia on HF risk is independent of other known risk factors. Analysis of datasets from populations including individuals with dysglycemia suggests the pathogenic role of hyperglycemia on left ventricular function and on the natural history of HF. Despite substantial epidemiological evidence of the relationship between diabetes and HF, data from available interventional trials assessing the effect of a glucose-lowering strategy on CV outcomes are limited. To provide some insight into these issues, we describe in this review the recent important data to understand the natural course of CV disease in diabetic individuals and the role of hyperglycemia at different times in the progression of HF.