Objective Health and related claims on food labels can support consumer education initiatives that encourage purchase of healthier foods. A new food Standard on Nutrition, Health and Related Claims became law in January 2013. Implementation will need careful monitoring and enforcement to ensure that claims are truthful and have meaning. The current study explored factors that may impact on environmental health officers' food labelling policy enforcement practices. Design The study used a mixed-methods approach, using two previously validated quantitative questionnaire instruments that provided measures of the level of control that the officers exercised over their work, as well as qualitative, semi-structured, in-depth interviews. Setting Local government; Australia. Subjects Thirty-seven officers in three Australian states participated in semi-structured in-depth interviews, as well as completing the quantitative questionnaires. Senior and junior officers, including field officers, participated in the study. Results The officers reported a high level of autonomy and control of their work, but also a heavy workload, dominated by concerns for public health and food safety, with limited time for monitoring food labels. Compliance of labels with proposed health claims regulations was not considered a priority. Lipsky's theory of street-level bureaucracy was used to enhance understanding of officers' work practices. Conclusions Competing priorities affect environmental health officers' monitoring and enforcement of regulations. Understanding officers' work practices and their perceptions of enforcement is important to increase effectiveness of policy implementation and hence its capacity to augment education initiatives to optimize health benefits.