Efficient energy transfer is key to the functioning of many energy-conversion devices, including those used in photocatalysis, bioimaging, sensing, solar energy harvesting, and light-emitting displays. With almost unlimited possible combinations of materials with different luminescence properties, energy transfer strategies offer infinite possibilities for the design of efficient X-ray imaging scintillators. Therefore, to improve the scintillation performance of organic materials, our group recently developed a series of high-performance energy transfer-based scintillators using different types of X-ray sensitizers (including organic materials, perovskites, and metal-organic frameworks (MOFs)) and emission centers (including fluorescent, phosphorescent, and thermally activated delayed fluorescence (TADF) chromophores). Moreover, the detailed energy transfer mechanisms were well investigated through different steady-states and time-resolved spectroscopic measurements, as well as high-level theoretical calculations.