<p dir="ltr">Undernutrition affects millions of children in low- and middle- income countries, causing poor growth, poor development, and increased risk of mortality. Many nutrition-sensitive interventions for rural areas increase household access to nutritious foods through increasing home production, a strategy that has small positive effects on child diets. However, there is growing evidence that local markets are also important for dietary quality. Despite the importance of rural markets, the rural food environment and food purchasing practices among rural households are not well-characterized in the literature. It is possible that promoting improved household food purchase practices is an effective method for improving child nutrition in rural areas. Tanzania experiences a high prevalence of undernutrition among children under the age of 5 years, particularly among rural populations. This dissertation utilizes data from the Engaging Fathers for Effective Child Nutrition and Development in Tanzania (EFFECTS), a cluster randomized controlled trial that was conducted in rural Mara, Tanzania. The EFFECTS trial promoted improved diets through both home production and through food purchases through a social and behavior change strategy. We measured changes in dietary diversity (a proxy for diet quality), children’s nutrient intake adequacy, and diversity of foods purchased and produced. This dissertation presents evidence that food purchase diversity is positively associated with dimensions of the rural food environment, including high market food diversity (+0.37 food groups, p=0.01), living within 30 minutes of a market (+0.36 food groups, p=0.001) and household purchasing power (+0.14 food groups per additional million Tanzanian shillings spent by the household, p<0.001). In turn, purchase diversity is positively associated with dietary diversity (b=0.22, p<0.001), and intake adequacy of folate, vitamin B12, and calcium (all p<0.05) among children 9-23 months. Promoting food purchase diversity was effectively integrated into the EFFECTS interventions, resulting in purchasing +0.54 food groups at endline compared to changes in the control (p<0.01), which mediated 25% of the total improvement in child dietary diversity. In contrast, production diversity was associated with increased intake adequacy of vitamin A only (p<0.05), households produced +0.44 food groups at endline compared to control (p<0.05), and this mediated 15% of the total improvement in child dietary diversity. These findings suggest that promoting diverse food purchases, alongside diverse home production, is an effective way to improve children’s diets in similar settings.</p>