Household garden interventions are one of only a few agricultural interventions with a proven effect on nutritional outcomes. Such interventions potentially contribute to eight of the 17 Sustainable Development Goals. Despite the recent surge in interest, there remains a lack of knowledge about how to implement household garden interventions, and there is also a lack of understanding of the causal mechanisms by which they improve nutrition. This paper describes the World Vegetable Center's household garden intervention approach, which builds on more than 30 years of experience in this area. The model has three components: year-round production of nutrient-dense fruit and vegetables, awareness raising about nutrition and health, and strengthening of key support systems, including women's groups and seed systems. The intervention targets poor women, mostly in rural areas, in households vulnerable to the effects of micronutrient undernutrition. Robust evidence for all parts of the impact pathway is gathered through widespread use of randomized controlled trials. We illustrate our work with seven ongoing household garden projects in Africa and Asia. It is important that the research and development community pays closer attention to the potential of household gardening for food and nutrition security in developing countries.