Ternary nanocomposites (NCs) were obtained by melt-mixing maleic anhydride-modified polypropylene (gPP) with previously prepared polyamide-12 (PA12)/organically modified montmorillonite (OMMT) NCs. During melt-mixing, OMMT migrated from the PA12 phase to the gPP/PA12 interphase. Moreover, a critical concentration of OMMT was found to saturate the interphase and, at higher contents, the excess OMMT migrated to the gPP matrix. When compared with the unfilled gPP/PA12 blends, the addition of OMMT caused a change in the microstructure. The average size of the PA12 dispersed particles in the NCs was found to be independent of the OMMT content. At OMMT contents below the critical concentration, that is, when the OMMT located at the interphase, Young's modulus remained practically unchanged and the ductile nature of the ternary NCs maintained. However, at higher OMMT contents, Young's modulus increased linearly and the NCs became brittle, due to the presence of OMMT in the gPP matrix. POLYM. ENG. SCI., 58:830-838, 2018. (c) 2017 Society of Plastics Engineers