We study the interfacial structure of a mixed dipolar liquid in contact with a metal surface by using a combined approach of the weighted density and the perturbative approximations. Both the molecular size and the dipole moment of various species can be unequal. The metal surface is treated by using the jellium model. Explicit numerical results are obtained for the interfacial structure of a binary dipolar liquid in contact with a metal surface of varying electron density. The theoretical predictions are compared with the results of Monte Carlo simulations and a good agreement is found for the inhomogeneous density, mole fraction, and polarization profiles of both the species in the interfacial region.