Achieving effective mechanical recycling strategies remains a major challenge for several reasons. Firstly, the thermo-mechanical degradation that polymers undergo during reprocessing, as well as the different degradation forms experienced during their service life, cause a severe modification of the material microstructure, ultimately leading to a progressive deterioration of their performance. On the other hand, due to non-fully accurate sorting technologies, low levels of cross-contamination are commonly encountered in recycled polymers. All these features result in recyclates with a heterogeneous morphology, significantly affecting their final properties and limiting their potential for high value-added future applications. This work aims to address these issues, by evaluating the coupled effect of cross-contamination and of the aging for polyethylene terephthalate (PET) containing low amounts of high-density polyethylene as a contaminant. In particular, pristine and cross-contaminated PET were subjected to photo-oxidative or thermo-oxidative treatments and the aged materials were reprocessed, aiming at simulating the real conditions of a typical mechanical recycling process. The obtained results demonstrated that cross-contamination has a limited effects on the processability and mechanical properties of reprocessed PET, either in photo-oxidative or in thermo-oxidative conditions. Finally, aiming at valorizing recycled cross-contaminated PET, the materials (both non-aged or subjected to photo- and thermo-oxidative treatments) were reprocessed through cast-extrusion, aiming at obtaining films potentially suitable for packaging applications. The processing was successfully carried out for cross-contaminated non-aged PET; otherwise, for achieving films based on the aged materials, the introduction of a chain extender was required for obtaining viscosity values adequate for film extrusion.