The tie-line data for the {4-methylpentan-2-one + 3=methylphenol, 4-methylphenol + water} ternary systems at 298.2, 313.2, and 323.2 K were measured under 101.3 kPa. The partition coefficient and separation factor were Computed in order to estimate the extraction capacity of 4-methylpentan-2-one, which indicated that 4-methylpentan-2-one has; an excellent performance in terms of extracting methylphenols from water. The activity coefficient models, nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC), were used to correlate experimental results, yielding root-mean-square deviations (RMSDs) below 0.5%. This indicated that both models represent the experimental data very well.