Experiments were conducted to establish the phase diagram for the ternary system containing (n-decane + water + triacetin) at T = 296.15 K and ambient pressure. Results indicated that this system belongs to Type 3 Treybal classification with a (liquid + liquid + liquid) equilibrium (LLLE) region. Five sets of NRTL parameters were determined using a combination of different objective functions and datasets (binary and ternary). A new objective function based on Gibbs energy minimization and a phase calculation scheme specific for Type 3 ternary systems were developed. Results indicated that the NRTL model can satisfactorily predict the ternary behavior of the system and could accurately correlate binary (liquid + liquid) equilibria (LLE), ternary LLE and ternary LLLE data simultaneously. Published by Elsevier Ltd.