Health behaviour change can be difficult to maintain. Action plans can address this issue, however, there has been little qualitative research to understand how to optimise action plan interventions. This study explored how people engage with a specific type of action plan intervention, the "volitional help sheet," in a cardiovascular disease (CVD) prevention context. Twenty adults in the target age for CVD risk assessment (45 to 74 years) with varying health literacy participated in interviews and created an action plan to change their behaviour. Transcripts were analysed using framework analysis. Participants described how engagement with plans was related to how personally relevant the target behaviour and the options within the plan were. Also important was participants visualising themselves enacting the plan when deciding which option to choose. Amongst participants who already engaged in a target behaviour, some did not perceive the plan was useful; others perceived the plan as a helpful prompt or a formalisation of existing plans. For some, the barriers to behaviour change were out of the scope of an action plan, highlighting the need for alternative supports. This study provides qualitative insights into unanticipated ways that people with varying health literacy use action plans, providing new guidance for future developers. SO WHAT?: Not all action plans are created equal. Careful selection of behavioural targets and plan options and encouraging users to imagine the plan may enhance user engagement. Alternative behaviour change strategies should be available if key barriers cannot be addressed by the plan.