Parents’ conceptions of child growth, health and malnutrition are culturally bound, making information about local understandings of malnutrition and its causes necessary for designing effective nutrition programmes. This study used ethnographic methods to elucidate cultural models of child care and malnutrition among the Yao of southern Malawi. Data were collected in six rural villages from 28 key informant interviews with village chiefs and traditional healers among others and 18 focus group discussions with parents and grandmothers of young children. For the Yao, lack of parental care is a key cause of poor child health and can lead to thinness (kunyililika) or swelling (kuimbangana). Parents are said to be careless if they are not attentive to the child's needs, are unable to provide adequate quality or quantity of food, or fail to follow sexual abstinence rules. Maintaining abstinence protects the family and failure to do so causes the transfer of ‘heat’ from a sexually active parent to a ‘cold’ child and results in child health problems, including signs and symptoms of malnutrition. These findings indicate that the Yao understanding of care is much broader than the concept of care during feeding described in the nutrition literature. In addition, the Yao note the importance of several key feeding practices supported by international agencies and understand the influence of illness on child nutritional status. These congruencies with the public health frame should be used together with information about the cultural context to design more socially and emotionally relevant care and nutrition programmes among the Yao.