Agricultural input subsidies, a form of social protection, are often considered an important means of improving agricultural productivity in low- and middle-income countries. However, their effectiveness and efficiency remains contentious with respect to productivity, economic and consumer welfare measures, as well as food and nutrition security. This is exacerbated by a weak evidence base, including no review focused on the impact of agricultural input subsidies on food security and nutrition. Further, where studies have considered nutritional outcomes of agricultural input subsidy interventions, this has often been in regard to changes in consumption of the targeted staple food, measured in terms of calorie consumption or a similar measure of changes in energy availability, ignoring other aspects of malnutrition, including impacts from dietary diversity. This wider consideration of impacts from dietary diversity is important, given the increasing recognition in nutrition policy of its importance. We address this gap in the literature with a review of the evidence on the impact of agricultural input subsidy programmes on nutrition and nutrition-related health in low- and middle-income countries, mapping this evidence against a conceptual framework of the mediating pathways.