In this work the phase diagrams for the ternary system water + trihexyltetradecylphosphonium dicyanamide + n-dodecane were determined at 298.15 K and 348.15K and atmospheric pressure. A triphasic region surrounded by two biphasic regions has been found. Due to the surfactant character of the ionic liquid, the system can be classified as Winsor Type III. The liquid-liquid and liquid-liquid-liquid equilibrium data of the corresponding immiscible regions were obtained. Focusing the work on surfactant flooding applications, the interfacial tensions between equilibrium phases of the binary and ternary systems were determined in presence or absence of salt. A comparison with other ionic liquids previously tested has been done on the basis of the position of the apex of the three-phase tie-triangle and the measured interfacial tensions. Other trihexyltetradecylphosphonium ionic liquids, with chloride or bis-(2,4,4-trimethylpentyl)phosphinate anions, showed more promising results. However, the knowledge of the phase diagram is of interest for processes that involve the co-existence of water, oil and ionic liquid, as triphasic catalysis or microemulsions applications. (C) 2015 Elsevier B.V. All rights reserved.