The modified Look Locker (MOLLI) sequence is the most widely used myocardial T1 mapping approach. In this 2D sequence, several T1-weighted images are acquired within a breath hold and used to create a T1 map. However, some patients are unable to sustain stable breath-holds which generates 3D motion between the T1-weighted images. While image registration can potentially be used to correct for in-plane motion, through-plane motion cannot be corrected and may introduce bias in T1 estimates. In this study, we sought to develop and assess a free breathing MOLLI sequence with real-time slice tracking and non-rigid image registration to reduce in-plane and through-plane motion effects.