Injoo obtained his B.A. in Asian History from Seoul National University, M.A. in Asian Studies and Ph.D. in Political Science from the George Washington University.
Prior to joining the University of Hong Kong, he was a postdoctoral fellow in the Princeton-Harvard China and the World Program (PHCWP) and visiting research fellow with the Princeton Institute for International and Regional Studies (PIIRS), Princeton University, where he worked on the PIIRS interdisciplinary project entitled "Power Transition, Security Cooperation, and International Order."
He also taught at the George Washington University, consulted for the Intergovernmental Group of 24 (G-24) and the United Nations Conference on Trade and Development (UNCTAD), and worked for the U.S. Congress (the Subcommittee on International Terrorism and Non-Proliferation).
His earlier research fellowships at the Shanghai Institute for International Studies (SIIS) and at the Chinese Academy of Social Sciences (CASS) were on Chinese foreign economic policy.
His teaching and research interests include international relations theory, international political economy, global governance, comparative politics, and Asian regionalism.