Despite their different economic backgrounds, Japan and Sri Lanka share similarities as island nations. As a developing country, Sri Lanka needs to identify the country’s existing situation of Plastic Waste Management (PWM) to improve the circularity in the sector. Japan’s existing PWM strategies are a pointer for Sri Lanka to improve the circularity along the plastic value chain. The main aspects that are considered in this study are quantitative data related to the plastic value chain, plastic recycling technologies, plastic recycling businesses, policies, regulations related to plastic waste management, and public awareness strategies in plastic waste management. The methodology relied on literature review and interviews. The main focus of these interviews was to fill the information gap that was identified during the literature review. Japan is practicing all the stages of the plastic value chain, including virgin plastic production, whereas virgin plastic production is absent in Sri Lanka. Technological and policy advancements like the application of Extended Producer Responsibility (EPR) in PWM in Japan can be used as a means of achieving circularity in the Sri Lankan PWM sector. The well-established informal plastic recycling industry in Sri Lanka is a significant feature compared to Japan’s formal plastic recycling industry.