After the COVID-19 pandemic, it has been observed that companies should employ sustainability in the packaging supply chain (PSC) to reduce waste and safeguard the environment. Packaging plays a major role in producing municipal waste, so we proactively need some major solutions to overcome this problem. Industrialized nations generate a significant part of packaging waste compared to developing nations. Developed countries are significantly trying to overcome this problem by implementing sustainable packaging in their businesses. By implementing sustainable packaging alternatives, concrete steps can be made to reduce the overall waste and pollution produced by traditional packaging, but in developing nations like India, it remains a challenge to explore this issue. This study attempts to discover the critical barriers to sustainability in PSC in developing economies. A total of 27 critical barriers were identified through the peer-reviewed articles and expert inputs, and these are categorized into six main barriers. The multi-criteria decision-making (MCDM) technique, called Best Worst Method (BWM), is employed to analyze the data obtained from the expert. The BWM method prioritizes the barriers to sustainability in PSC according to their degree of influence. The BWM results show that the most significant barriers were organizational barriers that must be taken as a major challenge towards achieving sustainability in PSC. After that, the significant barriers were the material barriers, financial barriers, logistical barriers, technological barriers, and independent barriers that have considerable impact on the performance of the enterprise. These results will help practitioners, industrial managers, and executives make planning, regulations and policies while implementing sustainability in PSC.