Medical management for children with type 1 diabetes mellitus, including insulin administration to control high blood glucose levels (BGL), is crucial. However, a child-controlled behavioural strategy, like physical activity, to maintain target BGL may be warranted. To demonstrate, pre- and post-activity BGL were collected for 73 children aged 8- to 14-years attending a diabetes camp. Change in BGL across one session of a free-play swimming activity was analysed. Average BGL was significantly reduced from 197.18 mg/dl to 177.78 mg/dl across one 45 min session, and male gender predicted larger reductions. With safety precautions and within the context of appropriate medical management, free-play activity could be used as a strategy for maintaining target BGL.