Cardiac involvement is an important cause of morbidity and mortality in Becker muscular dystrophy. Myocardial disease may progress despite relatively limited findings on conventional echocardiography, while cardiac magnetic resonance (CMR) provides detailed assessment of ventricular function and myocardial tissue characteristics with late gadolinium enhancement (LGE), parametric mapping and strain analysis. We report a case of 57 year-old man with genetically confirmed Becker muscular dystrophy who underwent CMR examinations 12 years apart. Follow-up imaging demonstrated progressive left ventricular remodelling, a decline in left ventricular ejection fraction and interval changes in the distribution and extent of myocardial fibrosis. This case provides a long-term within-patient comparison of Becker muscular dystrophy associated cardiomyopathy and illustrates the additional information provided by serial CMR in documenting progressive myocardial involvement over time.