Using experimental and literature data, theThe linear temperature-dependent interaction parameters of the Redlich-Kister (R-K) polynomial for binary subsystems of Al-Cu-Ni liquid alloy were optimizedoptimised using experimental and literature data. The activities of the binary sub-systems'subsystems' monomers were then computed using optimised parameters and validated against available experimental and literature data. The thermodynamic database of excess Gibbs free energy of mixing was theoretically reproduced for the ternary system at temperatures of 1773 K, 1873 K, 1973 K, and 2073 K, based on the General Solution Model (GSM), the Toop model, and the Kohler model. The surface tensions of the binary sub-systemssubsystems were computed employing Butler's equations and using theoretically computed values of the partial excess Gibbs free energies of monomers of the systems. Further, the optimised coefficients of R-K polynomials were obtained for the excess surface tensions of binary sub-systemssubsystems, which were then used to compute the surface tension of the ternary system based on the aforementioned models.