Phosphonium-based ionic liquids were used as new compatibilizers of polypropylene/polyamide blends using a standard extrusion process. Selected ionic liquids containing the same (trihexyl)tetradecylphosphonium-based cation but differing by the polarity of their counteranions were introduced at various concentrations in the blend. The anions selected have a special affinity with PP or PA6 phase (Figure 1). The effect induced by the presence of ionic liquids on the morphology, cristallization behaviour, thermal and mechanical properties of blends was highlighted. It seems that the addition of only 1wt% of ionic liquids induces a significant decrease of the size of the dispersed polymer phase (PA6 droplets) from 27 μm for the virgin binary PP/PA6 blends to 3 μm for PP/PA6/ILs ternary blends (Figure 2). It was also revealed that the final properties of the blends depend strongly on the polarity and concentration of ionic liquids introduced. When the counteranion was more hydrophilic, the compatibilization effect was more efficient as revealed by TEM microanalysis. The thermal stability of PP/PA6 blends was also enhanced in the presence of ionic liquids which depend on the amount of ILs introduced. The ductility of blends was also significantly improved in the presence of ILs without losing stiffness and particularly when a polar counteranion was used. Ionic liquids appear as promising materials that can offer the 'compatibilizer effect' for many immiscible polymer blends very frequently used in many industrial fields1. 1 E. Leroy, P. Jacquet, G. Coativy, A. Reguerre, L.D. Lourdin. Compatibilization of starch-zein melt processed blends by an ionic liquid used as plasticizer. Carbohydrate Polymers, 89 (2012), pp. 955-963.