BACKGROUND: There is increasing interest in brief and very brief behaviour change interventions for physical activity as they are potentially scalable to the population level. However, few very brief interventions (VBIs) have been published, and evidence is lacking about their feasibility, acceptability and which 'active ingredients' (behaviour change techniques) would maximise their effectiveness. The aim of this research was to identify and develop promising VBIs for physical activity and test their feasibility and acceptability in the context of preventive health checks in primary care. METHODS: The process included two stages, guided by four criteria: effectiveness, feasibility, acceptability, and cost. In Stage 1, we used an iterative approach informed by systematic reviews, a scoping review of BCTs, team discussion, stakeholder consultation, a qualitative study, and cost estimation to guide the development of promising VBIs. In Stage 2, a feasibility study assessed the feasibility and acceptability of the short-listed VBIs, using tape-recordings and interviews with practitioners (n = 4) and patients (n = 68), to decide which VBIs merited further evaluation in a pilot trial. RESULTS: Four VBIs were short-listed: Motivational intervention; Action Planning intervention; Pedometer intervention; and Physical Activity Diary intervention. All were deliverable in around five minutes and were feasible and acceptable to participants and practitioners. Based on the results of interviews with practitioners and patients, techniques from the VBIs were combined into three new VBIs for further evaluation in a pilot trial. CONCLUSIONS: Using a two-stage approach, in which we considered the practicability of VBIs (acceptability, feasibility and cost) alongside potential efficacy from the outset, we developed a short-list of four promising VBIs for physical activity and demonstrated that they were acceptable and feasible as part of a preventive health check in primary care. TRIAL REGISTRATION: Current Controlled Trials ISRCTN02863077. Registered 5 October 2012.