Public policy is increasingly informed by insights from the behavioural sciences. We highlight three aspects of behavioural public policy which can be incompatible with democratic ethics. First, policy-makers can use behavioural instruments such as nudges to steer citizens’ behaviour without giving reasons and by relying on non-participatory research methods. Second, behavioural public policy is frequently implemented in the form of administrative discretion by organisations which are not under direct democratic control. Third, behavioural public policy currently relies on a partial and narrow view of the behavioural sciences and is inattentive about value judgements already embedded in the research it draws upon.