BACKGROUND: Inappropriate marketing of human milk substitutes negatively influences efforts to protect breastfeeding. Although healthcare professionals can positively influence infant feeding decisions, government regulations permit manufacturers to communicate messages to them through advertising. RESEARCH AIMS: (1) To identify the extent of human milk substitute advertising in publications aimed at United Kingdom healthcare professionals and (2) to describe compliance with the International Code of Marketing of Breast-Milk Substitutes and United Kingdom Formula and Follow-on Formula Regulations. METHODS: This was a cross-sectional observational study. We reviewed publications targeting healthcare professionals working with families in the United Kingdom (N = 19). Quantity and type of human milk substitute advertisements, as a proportion of all advertising, in each publication were recorded. All unique advertisements were double assessed for compliance. RESULTS: Human milk substitute advertising was found in nine (47%) of the 19 publications (four affiliated with professional associations), making up 10.3% (n = 196) of these publications' total advertising. Of human milk substitute advertisements found, 65.4% (n = 110) were for products used to manage cows' milk protein allergy. Of the 32 unique human milk substitute advertisements found, none complied with the International Code of Marketing of Breast Milk Substitutes or United Kingdom Formula and Follow-on Formula Regulations. CONCLUSIONS: Many healthcare professionals' publications had non-compliant human milk substitute advertisements. There is an urgent need to ensure full compliance with international and local regulation in future advertisements and to consider whether advertisements are justified at all.