Increasing plastic pollution presents a significant challenge for humanity and ecosystems. Photothermal (light-to-heat) conversion has emerged as a promising strategy for recycling plastic waste. Upon light irradiation, photothermal agents provide intense thermal gradients localized to their surfaces, wherein the heat exceeds the degradation temperature (T_d) of polymers, inducing efficient depolymerization and/or degradation. Thermoplastics (including polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polycarbonate (PC)) and thermosets (epoxy resin) are subject to efficient degradation under mild conditions. This review summarizes some key results and advancements in polymer waste mitigation using photothermal conversion depolymerization and upcycling.