A middle-aged female patient presented with increasing dyspnoea following delivery of her second child. Echocardiography showed left ventricular (LV) dilatation and severe global impairment of systolic function (ejection fraction < 10%) but normal right ventricular (RV) dimensions. Plasma B-type natriuretic peptide level was elevated. Post-partum cardiomyopathy (PPCM) was considered and after initiating appropriate heart failure pharmacotherapy, her symptoms improved significantly. Cardiovascular MR showed RV free wall dyskinesia and aneurysms at the LV apex, RV free wall and RV outflow tract. Genetic analysis showed a C11842T substitution in the titin gene (TTN). This is the first case to propose an overlap syndrome of PPCM and arrhythmogenic RV cardiomyopathy.