The thermodynamic properties of the 3-chloro-N-phenyl-phthalimide in acetone+ methanol cosolvent mixtures were obtained from solubility data report in literature. The solubility was higher in near acetone and lower in pure methanol at all temperatures studied. A non-linear plot of ∆ from pure acetone up to x 1 soln H° vs. ∆ soln 2, Gerson G° shows a negative slope = 0.691. Beyond this composition, a variable positive slope is obtained with the exception of mixtures with x 1 = 0.121, x1 = 0.272 and x 1= 0.356 which is a not common trend in these systems. The preferential solvation of 3-chloro-N-phenyl-phthalimide by the components of the solvents was estimated by means of the inverse Kirkwood–Buff integral method, showing the 3-chloro-Nphenyl-phthalimide is preferential solvated bymethanol in more polar mixtures and by acetone in less polar ones.