The Coastal Highway Upgrade project in Belize represents a major advancement in sustainable infrastructure, transforming a 59-km stretch of flood-prone, unpaved road into a resilient, climate-adaptive highway. This project enhances connectivity, safety, and economic development in southern Belize by integrating innovative engineering solutions and environmental management. Key technical innovations include the use of geosynthetic materials for soil stabilization, advanced drainage systems to mitigate flooding, and elevated roadbeds to ensure continuous operation during extreme weather events. In addition, the project incorporated solar-powered streetlights and traffic management systems, reducing reliance on fossil fuels and aligning with Belize’s renewable energy goals. Environmental considerations were central to the project, with comprehensive Environmental Impact Assessments (EIA) guiding the implementation of bioengineering techniques, sediment traps, and wildlife corridors to protect biodiversity. Social and economic sustainability were also prioritized, with the project creating jobs for local communities, offering training, and improving access to essential services. The project addressed key Environmental, Social, and Governance (ESG) challenges, balancing development with ecosystem protection and community engagement. By adopting a multidisciplinary approach to design, construction, and management, the Coastal Highway Upgrade demonstrates how megaprojects can achieve sustainable development goals while mitigating environmental risks. This paper highlights the project’s technical, environmental, and socio-economic contributions, providing valuable insights for future infrastructure projects in regions facing similar challenges, as well as the pivotal role of the adoption of the Building Information Modeling (BIM) in order to ensure completeness, reliability and compliance of the project, then consistency throughout the entire construction process.