Securities regulation and investor protection are fundamental pillars for the development of efficient capital markets. This study examines the legal and institutional framework governing investor protection in Nigeria’s capital market and evaluates its implications for corporate finance. Adopting a doctrinal methodology, the paper analyses the provisions of the Investments and Securities Act (ISA) 2025, the Securities and Exchange Commission (SEC) Rules, and related regulatory instruments. It argues that robust investor protection enhances market integrity, reduces information asymmetry, and lowers the cost of capital, thereby promoting corporate financing and economic growth. However, despite notable regulatory improvements, challenges such as weak enforcement, limited investor awareness, and persistent market abuse continue to undermine investor confidence. The study concludes that strengthening enforcement mechanisms, improving disclosure standards, and enhancing investor education are essential for achieving sustainable capital market development and efficient corporate financing in Nigeria.