Kinetic mechanisms of carbon transport to ultra-low carbon (ULC) steel from magnesia-graphite ladle refractories were investigated through laboratory dip tests with commercially available ladle refractories in a vacuum induction furnace. The effect of refractory carbon content on carbon transfer was investigated by using refractories with carbon contents between 4-12 wt%. The influence of slag was also investigated by using slag free and slag containing dip tests with varying MgO content. Carbon transfer is controlled by steel penetrating into the refractory and dissolving carbon when no slag is present. The rate controlling step of this mechanism is convective mass transfer of carbon into the bulk steel. The mass transfer coefficient for carbon transfer was found to be approximately 1∙10^(-6) m/s. Corrosion of the refractory controlled the carbon transfer when slag was present. The mass transfer coefficient of MgO into slag was found to be 8∙10^(-6) m/s for 10 wt%C bricks and 12∙10^(-6) m/s for 4 wt%C bricks. The calculated carbon pickup based on these mechanisms was in good agreement with the measured carbon pickup which supports the proposed mechanisms.