Play is viewed as central to learning in the early years despite a lack of empirical evidence to support this. Most research has concentrated on adult definitions of play which fail to capture the intrinsic quality of playfulness. To achieve this it is necessary to elicit children’s definitions of play. The research discussed in this paper utilises children’s definitions of play to create formal and playful practice conditions to demonstrate the links between playfulness and learning. In addition, analysis of videotaped observations indicates behavioural differences according to whether children participate in playful or formal practice conditions. These findings support a behavioural threshold and fluency theory of play. Children in the playful condition exhibited more fluent and purposeful problem solving behaviours than children in the formal condition. Implications for practitioners in educational settings are outlined.