The present research work has evaluated the equilibrium solubility data of benzoic acid in monosolvents (benzyl acetate and benzyl benzoate), in binary systems (benzyl alcohol + toluene), (benzyl acetate + toluene), and (benzyl benzoate + toluene) in the temperature range 288.15-328.15 K, and in ternary systems (benzoic acid + phthalic acid + benzyl alcohol/methanol) at two different temperatures 298.15 and 308.15 K by varying the mole fraction of the binary mixture using high-performance liquid chromatography. Solid-liquid phase equilibrium data for the ternary system were measured using the isothermal saturation method and the ternary solubility data (saturated liquid and wet solid phase) were used to construct the isothermal phase diagrams. The two pure solids formed in the ternary system were distinguished by Schreinemaker's wet residue method at the corresponding temperatures. The experimental solubility data of benzoic acid in monosolvents and binary systems from this work were fit to various thermodynamic models reported in the literature such as the Buchowski equation and the Jouyban-Acree model. The Wilson model was also fit to investigate the effect of binary interaction parameters on the solubility of ternary systems. The experimental solubility data of benzoic acid in the solvents were in good agreement with the calculated values obtained through the thermodynamic models. The solubility data and phase diagram for the ternary systems show more practical application for the obtained benzoic acid and phthalic acid pure regions. For the ternary system that consists of methanol, pure regions were larger compared to that of the system with the benzyl alcohol as a solvent. Thus, the Wilson model was successful in explaining the experimental phase behavior of the ternary system, which was reflected in the minimum root-mean-square deviation value of 0.0086 for methanol at 298.15 K.