Background Miyoshi myopathy (MM) is a type of distal myopathy characterized by an early adult onset in an autosomal recessive form. MM is caused by mutations in the dysferlin gene (DYSF) on chromosome 2p13. Cardiomyopathy is one of major clinical manifestations in other muscular dystrophies and an important prognostic factor. Although dysferlin is highly expressed in cardiac muscle, no significant cardiac involvement has been reported in MM. This study sought to evaluate occult cardiac dysfunction in MM. We hypothesized that early myocardial dysfunction can be detected by echocardiographic myocardial strain imaging (MSI) and cardiac magnetic resonance imaging (CMR). Methods Five consecutive MM patients (3 males and 2 females) in whom we detected the DYSF gene mutation were included. None of the patients showed special cardiac history, signs and symptoms of overt heart failure. Myocardial Strain Imaging (MSI) and cardiovascular magnetic resonance imaging (CMR) were performed. MSI was obtained from Automated Function Imaging technique. Results All patients had normal LV systolic function. However, global peak systolic longitudinal strain (PSLS) was decreased in 3 patients and segmental PSLS was decreased 4 patients. In CMR, 1 patient showed thinning of Left ventricular wall and 4 patients had fibrosis in delayed image. The reduced PSLS lesion in MSI was tend to identify with portion which showed fibrosis in CMR. Conclusion Patients with MM showed subclinical to overt involvement of the heart. MSI and CMR are sensitive methods of assessing the presence of myocardial dysfunction prior to the development of any cardiovascular symptoms. The prognostic significance of these findings warrants further longitudinal follow-up.