Islands have been a focal point of sustainable development efforts. To understand the dynamic evolution of island sustainability is of great importance. In this study, a capital-based approach is piloted for measuring sustainability in Chongming Island along with its interactions with nearby mainland Shanghai, and to estimate the dynamic changes along with its responsible drivers. Initially, as per the capital-based approach, a three-tier indicator system with 31 indicators is developed to reflect sustainability by five capitals, namely, natural, social, human, financial and physical capitals. Subsequently, a detailed analysis is conducted to analyze the dynamic changes of each capital from 2000 to 2017 for both Chongming and mainland of Shanghai. Results show that: natural, physical and financial capitals followed a significant increasing trend, whereas a slight decline was observed in social capital. Also, no specific trend was noted in human capital for both study regions. Furthermore, as compared to the island, mainland seems to develop a higher sustainability for the respective time span. It is recommended that Chongming Island should focus on strengthening social and human capitals in the future. A wider and new public-private partnership is encouraged to improve public participation. This framework clearly depicts the dynamic evolution of sustainability, would help stakeholders to identify the restricting elements hindering the overall sustainable development, make it understandable and comparable for decision-makers to monitor gaps and proposing initiatives to reduce inequalities.