The problem of temperature jump in a multicomponent gas mixture is considered and a variational result valid for the Boltzmann equation and arbitrary gas surface interaction law is given. From this general result, a particularly useful expression for the monatomic binary gas mixtures and Maxwellian diffuse specular reflection is deduced. Explicit results for the He‐Ar mixture are given by using the Lennard‐Jones potential. Generalizations to the polyatomic gases are also discussed.