Purpose: The study aims to investigate the impact of capital structure on the financial performance of Indonesia's dual banking system, encompassing Conventional Commercial Banks (BUK) and Sharia Commercial Banks (BUS). Methodology/Approach: Utilizing panel data regression, the study examined 9 Conventional and 9 Sharia banks in Indonesia from 2013 to 2019. Key metrics included ROA, ROE, EAR, DER, company size, and economic growth. Results/Findings: EAR, DER, and economic growth positively and significantly impacted the ROA and ROE of conventional banks. For Sharia banks, company size and economic growth had a positive impact, while EAR and DER negatively influenced ROA and ROE. Conclusion: This research highlights the differing impacts of capital structure on financial performance between conventional and Sharia banks in Indonesia, demonstrating that while economic growth benefits both, the influence of capital structure varies, especially for Sharia banks. Limitations: The study is limited by the number of banks sampled (9 BUKs and 9 BUSs) and the timeframe (2013-2019), which may affect the generalizability of the results. Contribution: Offers critical insights for policymakers and bankers in optimizing capital structure strategies in Indonesia's dual banking system.