Gamma-delta T-cells are usually minor component of peripheral blood and lymphoid tissues, but may play an important role in autoimmune diseases. We here describe the first case of dilated cardiomyopathy (DCM) with heart infiltration by mostly gamma-delta T-cells, who improved significantly by steroid therapy. In general, steroid therapy has only a little effect on DCM, however these findings might have implications with respect to the selection of patients who might respond to immunosuppressive therapy.