Increasing on-farm production diversity and improving markets are recognized as ways to improve the dietary diversity of smallholders. Using instrumental variable methods to account for endogeneity, we study the interplay of production diversity, markets and diets in the context of seasonality in Afghanistan. We confirm an important seasonal dimension to the interplay. Improved crop diversity over the year is positively associated with dietary diversity in the regular season, but not in the lean season. Livestock species diversity remains important for dietary diversity throughout the year, but particularly so in the lean season when the influence of cropping diversity is low. Market aspects become important for dietary diversity specifically in the lean season.