Solubilities of different transition metals in WC in cemented carbides at around 1700 K were determined with atom probe tomography. Ta had the highest solubility, followed by Nb, Cr, and V, all with atom fractions in the 10−3 range. Ti and Mn showed lower, yet detectable, solubilities in the 10−6 or 10−5 range. Zr and Co solubilities were too low to be measured. The results were compared with the theoretically calculated solubilities using density functional theory. These calculations predicted that Ta, Nb, V, and Cr should have the highest solubility, all in the 10−4 or 10−3 range. Ti was predicted to have a lower solubility (10−5 range) and Co, Hf, and Zr even lower (10−8 or 10−7 range).