The red blood cell distribution width (RDW) is a measure of the variation of red blood cell (RBC, also known as erythrocytes), which is typically used in combination with mean corpuscular volume to diagnose anemia. Recently, a number of studies have shown that an increased RDW is a strong and independent predictor of prognosis in cardiovascular disease (CVD). Although the mechanism is still unclear, nevertheless, RDW is an easy, inexpensive, and routinely reported test which might supply diagnostic and prognostic information for patients with CVD. This article reviewed the promising progress of RDW application in cardiovascular disease.