Investment in agriculture is widely recognized as crucial for economic growth, poverty reduction and improved food and nutrition security. Although several estimates have been made of how much investment is needed in agriculture to achieve production or food security goals, no source to date has attempted to estimate the total amount of public and private investment that is actually made in agriculture. This paper does so using the most up to date and comprehensive international datasets available. It provides estimates of the relative size of investments from different sources for 76 low- and middle-income countries. Comparing the relative magnitudes of agricultural investment flows shows that the private sector is by far the largest investor in agriculture. This has important implications for policy: while funding of public investment in agriculture remains essential, in order to spur agricultural development, the focus of governments and international organizations must broaden. In addition to considering public investment in terms of dollar amounts, the international community and domestic governments must consider policies that help create the enabling environment that fosters more socially and environmentally sustainable private investment in agriculture.