This work reports the Calphad modelling of the Cr-Nb-Sn-Zr quaternary system. In a previous paper, the thermodynamic modelling of the CrNbSn system has been presented. Since no experimental data were available for the Cr-Sn-Zr ternary system, new experimental data are provided, within this study, on the isothermal section at 900 DC. A ternary C14 phase has been identified on the Sn-poor side of the phase diagram. In addition to these experimental data, Density Functional Theory (DFT) calculations are carried out in order to determine formation enthalpies of the stable and metastable phases. At last, the Special Quasirandom Structures (SQS) method is jointly used with DFT calculations in order to estimate the mixing enthalpies of the A2 and A3 binary solid solutions. Finally, these experimental and calculated data in addition to those from the literature, are used as input data for the Calphad modelling of the Cr-Zr, Nb-Zr and Sn-Zr binary systems and the Cr-Nb-Zr, Cr-Sn-Zr and Nb-Sn-Zr ternary systems. A complete database for the Cr-Nb-Sn-Zr quaternary system is provided.