Tissue characterization including identification and quantification of fibrosis and oedema plays an important role in many myocardial diseases. Conventionally T1 and T2 maps are acquired sequentially under several breath-holds. These approaches however achieve limited spatial resolution and coverage. Furthermore, partial volume effects at water-fat interfaces may affect the T1 and T2 quantification. In this work, we propose a free-breathing high-resolution whole-heart joint T1 and T2 mapping sequence with Dixon encoding which provides co-registered 3D T1 and T2 maps and complementary 3D fat images.