The present work reports on a thermodynamic modeling of the Mo-Pt system using a combined first-principles/ CALPHAD approach. First-Principles (FP) calculations are performed to obtain the enthalpies of formation for the four ordered phases of the system (A15, B19, D0 19 and MoPt 2 ) at 0 K. The liquid, bcc, fcc and hcp phases have been modeled as substitutional solutions where the excess term is in the form of the Redlich-Kister polynomial. The four ordered phases are modeled using the NACEF approach taking into account the three order-disorder transitions (B19/A3, D0 19 /A3 and MoPt 2 /A1). FP calculations, experimental phase equilibria and site occupancies data are used to evaluate the model parameters. The thermodynamic description of the Mo-Pt system obtained in this work agree well with all the available data with a limited number of parameters used.