The purpose of this papaer is to study the impact of CEO characteristics and board of directors' traits on corporate financial performance. The study sample covers 366 U.S. companies listed on the S&P 500 over the period 2005-2022. Specifically, we explore two CEO attributes: CEO compensation and CEO duality. As for the board of directors' characteristics, we focus on board independence, gender diversity, directors' specialized expertise, the frequency of board meetings, and the existence of a CSR committee. The results show that some governance practices including the dual role of management, gender diversity on the board, and the presence of a CSR committee, can enhance financial performance. Conversely, elements such us board independence and high CEO compensation negatively affect performance. Additionally, some factors for example board meeting frequency and the importance of specific skills on the board are not significant. Internal governance is essential to corporate governance, encompassing the mechanisms and practices that ensure effective and responsible management. Its main objective is to improve financial performance by ensuring informed strategic decisions and establishing appropriate controls. The relationship between internal governance and financial performance is a subject of major interest to researchers and practitioners alike. It is generally accepted that strong internal governance mechanisms promote sustainable and optimal performance, although this relationship is complex and influenced by a variety of factors specific to each organization. Key internal governance mechanisms include board structure, risk management practices, internal control systems and executive compensation policies. A well-constituted board, made up of independent and competent members, is crucial for effective oversight and can have a positive impact on financial performance. Similarly, robust internal control systems ensure the integrity of financial information and reinforce investor confidence. Numerous studies have attempted to evaluate this complex relationship, highlighting the importance of internal governance mechanisms in promoting sustainable and optimal financial performance. For example, Shleifer and Vishny (1997) defined corporate governance as a set of mechanisms that allows capital providers to ensure shareholder profitability. This definition underscores the essential role of governance in creating value for stakeholders. A central aspect of this relationship is the structure of the board of directors, which directly influences strategic decisions and the oversight of management. According to a study by Yekini et al. (2015), a board composed of independent and competent members fosters better information disclosure, thereby improving firm performance. Similarly, research conducted by Rosenstein and Wyatt (1990) demonstrated that the presence of independent directors positively impacts financial performance and stock market valuation. Furthermore, internal control systems play a critical role in ensuring the accuracy and reliability of financial information. Studies such as those by Beasley (1996) have revealed that robust internal control systems reduce the risk of fraud and errors, thereby strengthening investor confidence and contributing to better financial performance. Executive compensation policies also represent a key aspect of internal governance. According to Jensen and Murphy (1990), compensation systems aligned with performance criteria can incentivize executives to make sound strategic decisions, leading to improved firm performance. Soumaya Abbassi & Siwar Ellouz 102 The issue of this research revolves around the relationship between financial performance and corporate governance, posing the following central question: how do governance practices influence the financial performance of companies? The objective of this study is to analyze the impact of internal governance mechanisms on this performance. To structure this work, the second section provides a literature review and hypotheses development highlighting the influence of the characteristics of leaders, such as compensation and CEO duality, as well as that of the board of directors, taking into account factors such as independence, diversity, specific competencies, meeting frequency, and the CSR committee. The third section presents the adopted methodology, the fourth section is dedicated to the analysis and discussion of the data, and finally, the fifth section concludes the study by summarizing the main findings. 2-Literature review and hypotheses development