Between 2014 and 2019, Vietnam’sLai Cao Mai Phuong economic growth rate consistently exceeded twice the global average. Even amid the COVID-19 pandemic in 2020, Vietnam remained one of the few countries that sustained growth. This raises questions regarding the policy environment supporting business performance, enabling firms to continue expanding and contributing to economic development. This study investigates the effect of capital structure on the performance of non-financial enterprises in Vietnam—a developing economy. The research focuses on firms operating in the Food and Beverage, Steel, and Energy sectors during the 2017–2020 period, as these industries represent a significant proportion of Vietnam’s stock market and are classified as non-financial. Balanced panel data regression models are applied across all three sectors, using two distinct regression equations. After controlling firm-specific variables, such as asset growth, the ratio of fixed assets to total assets, revenue growth, size, and liquidity, the findings indicate that capital structure negatively affects firm performance in both the short and long term across all industries analyzed. These results suggest that Vietnamese firms should give priority to internal financing rather than relying heavily on debt. Moreover, to enhance operational efficiency, Food and Beverage firms should prioritize investment in fixed assets, while Steel and Energy firms should focus on boosting revenue and asset growth. Increasing firm size and asset accumulation are also recommended for all three sectors to improve performance outcomes.