The presence of fragmented QRS is a known marker of heterogeneous ventricular activation around the myocardial scar area. We validated whether fragmented QRS shows any association with ventricular dysfunction, fibrosis, or ventricular arrhythmias in patients with Duchenne muscular dystrophy (DMD). Thirty-seven patients with DMD were evaluated using electrocardiography (ECG), echocardiography, cardiac magnetic resonance, and 24-h Holter monitoring. Associations between fragmented QRS and ventricular dysfunction, fibrosis, or ventricular arrhythmia were investigated. Fragmented QRS complexes were present in 31 of 37 (83.7%) patients, and they were associated with a significantly lower left ventricular ejection fraction along with an increased left ventricular Tei index as evaluated by echocardiography, and more frequent ventricular arrhythmia as indicated using 24-hour Holter monitoring compared with patients without fragmented QRS. The number of leads with fragmented QRS correlated negatively with left ventricular ejection fraction both using echocardiography (r = −0.616) and CMR (r = −0.516). Further, the number of leads with fragmented QRS showed a significant correlation with several other echocardiographic measurements (mitral Em and Sm, and left ventricular Tei index), and 2-dimensional speckle-tracking echocardiography derived global left ventricular longitudinal strain. The frequency of ventricular arrhythmia observed using Holter monitoring showed a significant positive correlation with the frequency of fragmented QRS on ECG (r = 0.674). There was a positive trend of correlation between fragmented QRS and the amount of myocardial fibrosis as assessed by late gadolinium enhancement using CMR, but the statistical significance of the relationship was low (r = 0.433, p = 0.056). Fragmentation of QRS complexes is associated with degrees of left ventricular dysfunction, fibrosis, and ventricular arrhythmias in patients with DMD.