Osteopontin (OPN), also known as 44kDa bone phosphoprotein, sialoprotein I, secreted phosphoprotein I, 2ar, uropontin, and early T-lymphocyte activation-1 (Eta-1), is a multifunctional protein. OPN has been found to be expressed in various cell types and species with many physiologic and pathologic functions. OPN has emerged as a potential biomarker and mediator in cardiovascular disease. In this review, we will discuss the roles of OPN in cardiovascular disease, specifically in vascular and valvular heart disease, myocardial infarction and heart failure.