The regulation of unhealthy food marketing is a highly contested space that involves a diverse range of actors and institutions. There is a paucity of research on the strategies used by the different actors to influence these policies. This study examined the use of authority by different regulatory actors to influence food marketing policies. We conducted semi-structured interviews with (N = 24) government, industry, civil society and technical experts involved in the regulation of food and beverage marketing in Australia. We identified five types of authority: institutional, delegated, expert, principled and capacity-based authority. Actors from the advertising, food and media industries claim more authority than technical experts, civil society, and government actors, suggesting that industry actors have multiple pathways to influence policy. The industry's claims of delegated and institutional authority are highly contested by civil society, technical experts, and state/territory government actors and recognised by federal government actors. Claims of circumscribed institutional authority are common among federal government actors such as the National Department of Health, Australian Media and Communications Authority and Food Standards Australia New Zealand. The assertions of authority observed in this study highlight the fragmented manner of the Australian food marketing regulatory system and have implications for which actors should be held accountable for the current challenges in the governance of food marketing policies.