The compatibilizing effect of the ionomer, polystyrene-co-sodium acrylate) (PSSAc), on immiscible blends of polystyrene (PS)/polyamide 6 (PA6) was studied by mechanical tests and scanning electron microscopy. The PSSAc acts as an effective compatibilizer because both the deformation at break (%) obtained by tensile stress-strain tests and the impact rupture energy are larger in blends containing small amounts of PSSAc. The morphologies of the fractured surfaces produced by tensile stress-strain tests of blends with or without the ionomer confirm that PSSAc increases the interfacial adhesion between PS and PA6 phases. (C) 2004 Wiley Periodicals, Inc.