This study analyzes the effects of corporate ownership structure on research and development (R&D) investment. An empirical analysis of 159 firms listed on the Korea Stock Exchange revealed that managerial ownership and foreign shareholder ownership are significant determinants of R&D investment. Additionally, foreign shareholder ownership was found to moderate the effect of managerial ownership on R&D investment. However, the ownership shares of major shareholders and institutional investors were found to have no significant effect on R&D investment. The paper concludes with a discussion of the implications of these findings and directions for future research.