PurposeThe purpose of this paper is to evaluate the ability of a social marketing intervention to provide families with specific nutrition information, stimulate family discussions on the topic of nutrition, and encourage parents to make changes in their child‐feeding practices.Design/methodology/approachA postcard intervention was administered to families with children aged five to 12 years at three primary schools in Western Australia. Approximately two months later, an evaluation questionnaire was administered to the three intervention schools and a control school.FindingsIn total, 229 usable questionnaires were returned, representing a 22 percent response rate. In the intervention schools, almost half of the respondents reported discussing the contents of the postcards with their children and a third reported giving the cards to their children to read. The intervention was successful in encouraging a majority (60 percent) of respondents to make at least one favourable change to their child‐feeding practices, in line with the recommendations provided.Originality/valueThe study demonstrated that a simple and cost‐effective social marketing intervention can encourage family discussions on the topic of nutrition and favourably influence parents' child‐feeding practices.