Research in Bangladesh shows that malnutrition among infants and young children is most severe in urban slums. We examined the root causes of malnutrition as perceived by pregnant women and community health workers. We conducted 10 focus group discussions in the slums of Dhaka in 2008 and 2009. Participants accurately perceived inappropriate care, inappropriate environment, inappropriate food, and flooding to be major causes. Recurrent flooding has not traditionally been identified by experts as a cause of malnutrition. We recommend further research to address the nutritional risks flooding creates for vulnerable slum populations.