This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: The primary objective is to assess the effects of physical activity interventions for increasing physical activity in children aged 4 to 12 years in outside-school hours childcare settings (i.e. the hours of the day when formal school lessons have either not begun or have finished and/or during school holiday periods). Our secondary objectives are to assess the effects of interventions on markers of children's cardiovascular health, quality of life, process evaluation and to identify any unintended adverse outcomes (e.g. injuries, distress).