This work investigates the effect of ethylene-octene copolymer (EOC) as a compatibilizer for two virgin and two recycled polyethylene/polypropylene blends. In particular, a focus is made on the interfering effects of contamination in recycled materials. Scanning electron microscopy (SEM) shows that (i) recycled compounds have smaller domain sizes than virgin compounds, and (ii) addition of a compatibilizer is much more effective on domain sizes reduction in virgin compounds than in recycled ones. Conversely, transmission electron microscopy, coupled with energy dispersive X-ray spectroscopy, shows the presence of nano-size contaminants in both recycled blends. Such contaminants are considered responsible for the above mentioned observations in SEM. Mechanical characterizations are also in good agreement with morphological observations. Although recycled compounds containing EOC show improved deformability, the ultimate deformation of virgin compounds is much higher. (C) 2015 Society of Plastics Engineers