The scarcity of resources combined with the COVID-19 pandemic outbreak has forced the manufacturing companies to be more prudent in using their production resources such as raw materials, energy, and water. A lean sustainable production system is an effective Competitive Manufacturing Strategy (CMS) that enables companies to sustain their production by identifying the potential waste and pollution. This study aimed to propose a novel framework by combining Sustainable Value Stream Mapping (SVSM) by Hartini and Sustainability Index (SI) assessment model by Garbie to assess the contribution of lean sustainable CMS in enhancing manufacturing performance. An SVSM and pairwise comparison is used to measure the SI. The SVSM is applied to identify the waste, while the pairwise comparison is used to determine each performance indicator's weight. A case study is conducted in an Indonesian car manufacturing company to validate how the lean sustainable CMS improves the SI. The results of this study should guide the practitioners in a standard procedure for assessing the effectiveness of lean sustainable CMS. For academicians, the work provides empirical evidence of the positive impact of lean sustainable CMS practices on the SI.