Vietnam is among the top five nations most vulnerable to climate change, suffering annual economic losses of 0.8% to 1.2% of gross domestic product from natural disasters. The development highlights the acute need for a green finance framework supporting the country's goal of a net-zero emissions target by 2050. This current policy-relevant study examines Vietnam's green finance activities between 2015 and 2025, focusing on regulation frameworks, green bond growth, investor behavior, and the role of catastrophe bonds (CAT bonds) as a potential tool for building climate resilience. Using a mixed-methods approach involving qualitative policy analysis, quantitative trend review, case studies of two state-owned enterprises, and global market benchmarking, the research finds that green credit comprises just 4 to 5% of total loans and green bonds only 1.5% of the domestic bond market in 2023, limited by a missing green taxonomy, insufficient incentives, and low consumer engagement. It also uncovers behavioral barriers to adopting green financial products and recommends CAT bonds to mitigate climate risks. The study concludes that Vietnam should pursue regulatory reforms, market innovation, capacity building, and institutional collaboration to expand green finance, providing a model for other climate-vulnerable economies aiming for sustainability.