<p>Establishing a reliable atomic mobility database is crucial for accurately describing the solidification processes and conducting kinetic simulations of rare earth and transition-metal (RE-TM) alloy systems. However, experimental diffusion data in these systems are sparse, fragmented, and often inconsistent due to the high chemical reactivity of rare earth elements, magnetic effects, and limited temperature windows accessible in diffusion measurements. As a result, reported self- and impurity diffusion parameters frequently exhibit significant discrepancies, which hampers their direct application in mobility modeling. In this work, a critical assessment of self and impurity diffusion parameters in RE-TM (RE = rare earth elements; TM = Fe, Co, Ni, Cu) systems is carried out. Available experimental diffusion data in bcc, fcc, and hcp phases are re-evaluated. To compensate for the lack of experimental information, previous studies based on first-principles calculations, machine-learning predictions, and semi-empirical models were also evaluated. Computational results that were inconsistent with experimental data were scrutinized and excluded when necessary. Based on the assessment of experimental data, reliable activation energies and frequency factors were obtained, providing accurate atomic mobility parameters for RE-TM systems. This study presents a comprehensive evaluation of self-diffusion and impurity diffusion in RE-TM systems and the assessed parameters provide an atomic mobility dataset that can be used to support diffusion-controlled kinetic simulations in RE-TM systems.</p>