The surface tension of N-methyldiethanolamine in methanol, or in methanol aqueous solutions as a solvent, was measured at temperatures from 293.15 to 323.15 K. In ternary mixtures, five methanol + water blends with concentrations between 10 and 90% methanol were used as solvents, and the amine concentration varied from 0 to 50% mass, while in the methanol + N-methyldiethanolamine (MDEA) system, the amine concentration varied between 0 and 100% mass, at intervals of 10%. Experimental data were correlated with temperature and concentration by means of the Jasper equation, and the Jouyban-Acree and FLW models, respectively.