In Europe, about 20% of children are overweight. Focus on parental responsibility is an effective method in weight control interventions in children. In this systematic review we describe the intensity of parental involvement and behaviour change aimed at parents in long-term European childhood weight control interventions. We include European Union studies targeting parents in order to improve children's weight status in multi-component (parental, behaviour change and nutrition) health promotion or lifestyle interventions. The included studies have at least one objectively measured anthropometric outcome in the weight status of the child. Parental involvement was described and categorized based on the intensity of parental involvement and coded using a validated behaviour change taxonomy specific to childhood obesity. Twenty-four studies were analysed. In effective long-term treatment studies, medium and high intensity parental involvement were identified most frequently; whereas in prevention studies low intensity parental involvement was identified most frequently. Parenting skills, generic and specific to lifestyle behaviour, scored frequently in effective weight control interventions. To list parental skills in generic and specific to lifestyle, descriptions of the included studies were summarized. We conclude that intensity of parental involvement and behaviour change techniques are important issues in the effectiveness of long-term childhood weight control interventions.