Plastic wastes can partially or totally replace virgin polymers in several applications, leading to considerable savings in raw materials and energy. Among the various recycling techniques, mechanical recycling stands out due to the simple machinery required. A common route to mechanically recycle plastics is to blend them with virgin polymers. Different additives are generally used to improve the processability and final properties, and an increasing interest is being addressed to organoclays. The latter act as nonspecific compatibilizers for numerous polymer systems and could then be very useful in the recycling process, where the composition is often uncertain. On the other hand, multiple interfaces represent defect points in an immiscible polymer blend and should thus be minimized. The aim of this work is to prepare and characterize ternary blends with virgin polyolefins, namely high-density polyethylene (HDPE) and polypropylene (PP), as the major phases and polyethylene terephtalate (PET) ground from post-consumer bottles as the minor one. A conventional twin-screw extruder is used. The compositions and processing conditions are optimized in order to compound below the melting point of PET and obtain co-continuous blends of HDPE and PP with a well dispersed small amount of PET, which acts as solid filler. Analogous systems are prepared with the addition of clay nanoparticles in order to assess their influence on the structure and properties of the materials. According to wettability considerations, the PET should locate within the HDPE phase, the nanoparticles occupying the HDPE/PET interface. Such morphologies, which are visually inspected by scanning and transmission electron microscopy, are desirable since the problem of multiple interfaces is minimized. The mechanical and thermal properties of the blends are also investigated to correlate the macroscopic properties of the resulting materials to their nano- and microstructure.