Over the past four decades, IFPRI Japanese Researchers (IFPRI-JR) significantly contributed to the knowledge advancement for various agrifood system issues in ways that are central to IFRRI's mandates and complementary to the whole CGIAR system. This paper summarizes IFPRI-JR's key knowledge work, its evolution over time, and its collective contributions. In earlier years especially up to the 2000s, various policy and market analysis tools were applied to agricultural policy reforms and price policies in Japan and elsewhere. More recently, to respond to the food crisis in 2007-08, IFPRI-JR's research contributed to building empirical evidence on agrifood system policy issues in developing countries, including identification of key market failures and the appropriate role of the public sector in public goods provision in the presence of externalities and economies of scale. Over time the analytical scope expanded to institutional issues on resource management and markets, human capital formation, gender issues, agrifood system transformation, food and nutrition security. Finally, promising Japanese technologies and know-how were (i) identified for sustainable agrifood system development, and (ii) transferred to developing countries in the field of global nutrition security and their effectiveness shown. Collectively, IFPRI-JR have a long track record of addressing emerging as well as long-term structural issues, in both Japan and the world at large.