Blends of organically modified montmorillonite (OMMT) with poly(ethylene terephtalate) (PET) waste and poly(methyl methacrylate) (PMMA) were prepared by melt mixing. The morphology of PET/PMMA nanocomposites with different OMMT contents was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nonisothermal crystallization temperatures of nanocomposites were also examined by DSC. TEM observations and XRD patterns revealed that silicate layers were intercalated and well dispersed in the blend. Nanocomposites displayed better mechanical properties when compared with the unfilled blend. DMA analyses also showed efficient mixing of the two immiscible polymers and changes in glass transition temperature with the presence of OMMT. DSC analysis showed an enhancement in crystallization rate of nanocomposites and a decrease in cristallinity. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 129-137, 2010