Dilated cardiomyopathy (DCM) is a primary myocardial disease characterised by dilatation of the left or both ventricles and systolic dysfunction. DCM is generally considered idiopathic as underlying causes are rarely identified. It is however increasingly accepted that that DCM is the end result of different forms of myocardial insult related to genetic and environmental (viral, toxic and nutritional) factors. Recent information also raised increasing concerns over the role of diet on myocardial dysfunction, with cases of DCM being linked to certain types of foods (e.g. grain free). This lecture will include a review of the causes and clinical manifestation of DCM in dogs, focusing on specific breed differences, and an update on the diagnosis and treatment of DCM. We will also review and discuss recent information on the role of diet on myocardial dysfunction.