Interaction energies between substitutional 3d transition metal elements and an interstitial carbon atom in α iron are estimated using the first-principles calculation. Calculated interaction energies are in good agreement with the experimental values reported for Co, Ni and Cu, showing a repulsive interaction experimentally. However, the interaction for such elements as Ti, V, Cr and Mn are also estimated to be repulsive, although the interaction between these elements and a carbon atom is known to be attractive experimentally. This apparent contradiction may be due to a difference in the formation energy of carbide precipitation from the atomic pair interaction energy.