The thermal oxidation of polylactide–low-density polyethylene mixtures with additives of oxidized polyethylene as an analogue of recyclable materials is studied. It is found that the polylactide is oxidized more slowly than polyethylene, whereas the introduction of up to 30 wt % of oxidized polyethylene accelerates the thermal oxidation of the mixtures, with the physical and mechanical properties of the resultant materials remaining suitable for practical use. It is established that the presence of oxidized polyethylene has virtually no effect on the melting point of polylactide and polyethylene, somewhat increasing, however, the degree of crystallinity of the components of the blend.