Diarrheal disease in under-five children remains high in Sub-Saharan Africa; primarily attributed to environmental pathogen exposure through poorly managed water, sanitation, and hygiene (WASH) pathways, including foods. This formative study in rural Malawi used a theoretical base to determine the personal, social, environmental, and psychosocial factors that are to be considered in the development of an integrated intervention for WASH and food hygiene. Using a mixed methods approach, a stakeholder analysis was followed by data collection pertaining to 1079 children between the ages of four to 90 weeks: observations (n = 79); assessment of risks, attitudes, norms and self-regulation (RANAS) model (n = 323); structured questionnaires (n = 1000); focus group discussions (n = 9); and, in-depth interviews (n = 9) (PACTR201703002084166). We identified four thematic areas for the diarrheal disease intervention: hand washing with soap; food hygiene; feces management (human and animal); and, water management. The contextual issues included: the high level of knowledge on good hygiene practices not reflected in observed habits; inclusion of all family members incorporating primary caregivers (female) and financial controllers (male); and, endemic poverty as a significant barrier to hygiene infrastructure and consumable availability. The psychosocial factors identified for intervention development included social norms, abilities, and self-regulation. The resulting eight-month context specific intervention to be evaluated is described.