The study aimed to establish whether family characteristics and the health behaviour and illnesses of parents and children are associated with public health nurses' (PHNs') concerns about children's physical health and psychosocial development in the context of health examinations. Factors affecting children's health and well‐being should be identified as early as possible to provide children and families appropriate support. In 2007–2009, a cross‐sectional study in Finland collected information about PHNs' concerns, children's health and well‐being as well as the background factors affecting them during health examinations of preschool‐age children and school‐aged children (n = 4795). Associations between family characteristics, parents' and children's behaviour and diseases, and PHNs' concerns were assessed using logistic regression analysis. Overweight in children, the long‐term illnesses of both children and parents, and parental smoking were the factors most strongly associated with PHNs' concerns about a child's physical health whereas non‐nuclear family types, the father's low educational level and unemployment, the child's lack of sleep, and bullying were associated with concerns about the child's psychosocial development. The connections found demonstrate that health examinations should address factors that affect the whole family's well‐being so as to comprehensively promote children's health, growth and development.