Aim: This study aimed to investigate social, emotional and mental health and wellbeing aspects of playtime through child-led participatory action research in one school. Method: A stakeholder group involving the project facilitator (first researcher), school staff and four trained child co-researchers (aged 9 to 10) was established to facilitate the research. The co-researchers were supported to design and facilitate data collection and collaborative thematic data analysis. Findings: Five main themes emerged from analysis--the availability and nature of games, having someone to play with, how people treat each other, the importance of playtimes and views of the playtime rules. This research highlights interactions between the themes as important to children's social and emotional development, and mental health and wellbeing when accessing their right to play during playtime. Limitations: Research was completed on a single site. Repeating the design at another school might yield different results. While steps were taken to minimise power imbalances between the child participants and the project facilitator, it is acknowledged that these are difficult to overcome fully. Conclusions: This study highlights the importance of holistic playtime provision that acknowledges the interactions between themes in supporting children's wellbeing and social and emotional development. It illustrates that with appropriate training and support, children were able to effectively engage in research investigating playtime.