This study examines the roles of board composition, firm size, and earnings manipulation in determining firm value within the context of the LQ45 index, which comprises the 45 most liquid stocks in the Indonesian Stock Exchange. This study involves 45 companies listed in the LQ45 index. The number of samples in this study was 45 companies covering 5 years of data, so the overall number of observations was 225 company years. The findings reveal that independent commissioners and board size have significant positive effects on firm value, while the Corporate Governance Perception Index (CGPI) is not significant. Additionally, the study demonstrates that firm size significantly influences firm value. Earnings manipulation is found to mediate the relationship between corporate governance, firm size, and firm value. These results highlight the importance of board composition and firm size in creating value for stakeholders and emphasize the need to understand better and monitor earnings manipulation practices. The study offers valuable insights for investors, regulators, and policymakers in improving corporate governance and enhancing the integrity of financial markets.