The research examines the influence between Good Corporate Governance (GCG) represented by institutional ownership and public ownership on firm value. The study was conducted at 45 manufacturing companies listed on the Indonesia Stock Exchange during the period of 2015 to 2018. The sobel's test method was used in this research to identify the role of corporate social responsibility disclosure (CSRD) as a mediating variable on the influence of GCG on firm value. The results of this study indicate there is a positive influence of institutional ownership on firm value and this study cannot prove CSRD as a mediating variable of GCG and firm value.