In many developing countries, supermarkets are spreading rapidly at the expense of traditional food markets and shops. Changing retail environments and food choices may affect consumer diets and nutritional outcomes. Previous research suggested that supermarkets may contribute to rising rates of obesity. However, most existing research looked at adult populations. Here, we analyze effects of supermarkets on child nutrition with panel data from medium-sized towns in Kenya. Instrumental variable regressions show that supermarket food purchases significantly increase child height-for-age and weight-for age Z-scores. The effects on height are larger than the effects on weight. These are welcome findings, because child stunting continues to be a major nutrition problem in developing countries that is declining more slowly than child underweight. Supermarkets do not seem to be a driver of childhood obesity in Kenya. The positive effects of supermarkets on child nutrition are channeled through improvements in food variety and dietary quality.