A modified polyamide 6 has been used as compatibilizer in blends of polyamide (PA) and isotactic polypropylene (PP). PA was modified in the molten state by trimellitic acid (TMA) and n-octyl glycidyl ether by reactive processing. NMR and FTIR results show that TMA and the ether reacted with PA. Isothermal crystallization kinetics of the polymers in neat and blend states has been investigated by differential scanning calorimetry. Crystallization behavior of the polymers in neat state differs from that in blends. However, tendencies are the same for the constituents. The rate of crystallization is highest in unmodified blends and lowest in neat polymers while intermediate in modified blends. An investigation of surface and interfacial tension revealed that both surface tension of modified PA and interfacial tension between modified PA and PP decrease as compared to unmodified PA. These results are consistent with optical micrographs that show finer dispersions of particles in modified than in unmodified systems.