We report the 15th documented case of atrial dilated cardiomyopathy associated with the homozygous c.449G>A (p.Arg150Gln) NPPA mutation.<h4>Case summary</h4>A 31-year-old woman presented with persistent atrial fibrillation, biatrial enlargement, and junctional rhythm. Here, NPPA is linked to atrial fibrillation.