The "Children's Engagement Behaviour Framework" was developed to describe young children's engagement with science exhibits and how their behaviour is related to learning about the exhibits. The "Framework" was synthesised from frameworks in research literature related to family learning and the nature of play. It describes three categories of epistemic behaviour and two categories of ludic play behaviour. Field-testing in a playgroup environment where young children engaged with science exhibits revealed that its five categories effectively captured the range of engagement behaviours children displayed. The "Framework" was used to code video-recordings of 20 children in five further playgroups, categorising 89 child-exhibit interactions lasting at least 30 s. The inter-coder agreement was 93% and differences were easily resolved. The highest level of epistemic behaviour was recorded at each exhibit and 29 instances of ludic behaviour occurred. Children were interviewed using stills from their video-recording to stimulate discussion about exhibits. Epistemic behaviour was strongly related to learning about how the exhibit worked but ludic behaviour had no relationship with such learning. This research has demonstrated the relationship between observable epistemic behaviour and learning and provided a "Framework" for research into the engagement behaviour of young children. Practical applications of the "Framework" are discussed.