AimThe aim of the study was to describe the level, types and determinants of leisure time PA and exercise among children with type 1 diabetes and their parents.MethodsOne hundred twenty children aged 6–18 years with type 1 diabetes and 113 parents (n = 113) participated to this questionnaire‐based study at Northern Ostrobothnia District Hospital in Oulu, western Finland. All participants gave informed consent before entering this study.ResultsTwenty‐three per cent of the children exercised briskly for at least 7 h a week which corresponds to 60 min per day. The total PA occasions children had with a parent accounted for the children's total number of PA occasions in a week (β = 0.83, 95% CI 0.20–1.47) and total weekly hours of PA (β = 0.90, 95% CI 0.07–1.73). There was a positive association between total weekly hours of brisk PA and HbA1c (β = 0.65, 95% CI 0.02–0.13), while there was no such association with light PA (β = 0.42, 95% CI −0.04–0.87). Laziness, fear of unexpected glycaemic variability and tiredness were the most frequent barriers to PA in children.ConclusionMost of the children with type 1 diabetes did not reach generally recommended 60 min of brisk PA a day. Exercising with a parent was positively associated with children's weekly frequency and total hours of PA.