This paper presents a novel method for non-invasive mapping of thermal energy transport in three-dimensional (3D) printed structures using magnetic resonance imaging (MRI). Other techniques can only measure thermal transport at distinct locations or boundaries, while this new approach images thermal transport throughout a solid domain. The method utilizes a 3D printed structure filled with discrete microscale phase-change material (PCM) beads at 10% loading. When the encapsulated PCM in the beads undergo a solid-to-liquid phase transition during heating, it generates a distinct signal change that can be visualized using MRI. This method is demonstrated here in a cylindrical pipe where heated air flow passed through the center, heating the walls. The resulting MRI shows a clear visualization of the energy transport within the structure over time. Specifically, experimental images are generated in the transverse and longitudinal planes of the cylinder, allowing for the visualization of heat transfer within the cylinder walls. The MRI method is sufficiently fast to capture the time-dependent behavior. The results obtained using this method match expected computational fluid dynamics results, indicating the accuracy of the new measurement. The MRI-3D printing method can be extended to more complex geometries, including complex porous structures, wavy channels, and media with gradients in porosity/structure.