This study examines the impact of green bond issuance on financial performance, focusing on capital structure, profitability, and leverage on construction and energy industries in Vietnam. Using a Difference-in-Differences (DiD) approach, conducted in Python, this study analyzes financial data from 196 listed firms in Vietnam’s construction and energy sectors from 2019 to 2024, covering both before and after green bond issuance. The findings indicate that green bonds positively impact capital structure by lowering WACC and improving profitability through higher ROA. Their effect on leverage, however, is negligible. While green bonds influence the DTE ratio, the change is so minimal that it hardly causes any fluctuation in leverage structure. Issuing firms can thus maintain stable leverage without significant alterations to their debt levels. This research contributes empirical evidence on the financial benefits of green bonds in Vietnam, highlighting their role in addressing capital shortages and diversifying the range of financial instruments in capital markets. Building on these findings, this study offers recommendations for businesses, investors and policymakers on how to leverage green bonds to enhance financial performance while ensuring they fulfill their purpose-funding environmentally impactful projects.