Heart failure (HF) is one of the most important health problem that affects millions of people worldwide and like any other heart disease its evolution is influenced by the comorbidities that the patient has, such as diabetes mellitus (DM). So, it is necessary to study not only the aspects related to HF, but also the influence of DM in its evolution in order to choose correctly the treatment of HF. These two entities interest not only due to their high morbidity and mortality, but also they are two diseases that are difficult to manage, especially if they coexist. Therefore, the main aims of this review are: correlation between DM and HF, the influence of DM on evolution of HF and the highlight of basic changes of a diabetic heart in a patient with HF. Recent clinical trials reported that DM was associated with a 2-4-fold increase in HF incidence, even after adjusting for other cardiovascular risk factors. This can be explained by the modifications that the heart of a diabetic patient undergoes, such as inflammation, oxidative stress, lipotoxicity. Another theory that could explain the involvement of DM in the evolution of HF is the existence of a specific diabetic cardiomyopathy that includes: microangiopathy, abnormal myocardial metabolism and fibrosis. The microangiopathic changes leads to an alterated cardiac autonomic function and increases stiffness of the ventricular wall due to accumulation of advanced glycated end-products, which will worsen the diastolic function of the heart. It was observed that advanced glycated end-products correlate inversely with left ventricular ejection fraction and as a result it is related to the severity and prognosis of the disease. In advanced stages of diabetic cardiomyopathy is implicated interstitial and perivascular fibrosis that causes microvascular ischemia that contributes to contractile dysfunction. Therefore, observational studies confirm that diabetes remains a significant predictor in the development of a symptomatic HF at patients with left ventricular systolic dysfunction who have previously been asymptomatic. Analyzing the data from medical literature, I can conclude that DM is a major risk factor in the morbidity and mortality of HF. Also, the presence of DM in patients with HF increases the rate and duration of hospitalization, decreases ejection fraction b throughb different bmechanisms bofb heart bremodelation,  which bresults bin aggravation both symptoms and abmore worrying prognosis for patient.