Developing countries like India and Indonesia struggle with proper management of plastic waste, causing rampant plastic pollution that adversely impacts the ecosystem and potentially human health. In this study, life cycle assessment (LCA) was adopted to compare the environmental impact of end-of-life (EOL) treatment of 1 kg plastic waste in India and Indonesia based on the EOL mix, which includes mechanical recycling, co-processing in cement kilns, incineration, sanitary landfill, open dumping and open burning. Nine environmental impacts were considered, namely climate change, cumulative energy demand, water depletion and marine eco-toxicity, human toxicity, terrestrial acidification, fossil depletion, particulate matter formation and urban land occupation. Waste plastics EOL treatment in India was found to have a lower environmental impact than Indonesia among all nine categories, which was attributed to higher mechanical recycling rates in India. Hotspot analysis revealed that open burning is a major contributor to climate change, while landfills are the major contributor to marine eco-toxicity. A sensitivity analysis found that the percentage of plastic waste collection, percentage of uncollected plastic waste openly burnt, percentage of plastic rejects from recycling and percentage replacement of virgin plastic from recycled plastic granules were key sensitive parameters. The results of a future scenario analysis showed that further investments in mechanical recycling by 2030 can not only reduce mismanaged plastic waste, but also contribute towards the Paris Agreement carbon reduction pledges for both India and Indonesia. The results from this study can be used to support future waste management investment decisions in both countries.