This research aims to analyze the effect mechanisms of good corporate governance (GCG) consisting of an independent board of commissioners, institutional ownership, board of directors, audit committee, and managerial ownership on financial performance proxied by return on assets (ROA). The objects in this research are manufacturing sector companies listed on the Indonesia Stock Exchange (IDX) for the period 2019 to 2021. The population in this research was 217 companies. The sampling technique used in this research was purposive sampling. Based on the sample criteria that have been selected in this research, a sample of 37 companies was obtained during 3 years of observation resulting in a total of 111 sample data. The research method used is the descriptive statistical test, classical assumption test, and multiple linear regression analysis. The results of empirical research show that the independent board of commissioners and the audit committee have a positive and significant effect on financial performance. Meanwhile, institutional ownership, board of directors, and managerial ownership have no effect on financial performance.