Objective: To determine the effects of a six-month physical activity stimulation programme on social participation, self-perception and quality of life in children with cerebral palsy. Design: Multicentre randomized controlled trial with concealed allocation, blinded assessments and intention-to-treat analysis. Setting: Paediatric physiotherapy practices, special schools for children with a disability, and the child's own home. Subjects: Forty-nine children with spastic cerebral palsy (28 male), aged 7-13 years, able to walk with and without walking aids. Interventions: The intervention group followed a six-month physical activity stimulation programme involving counselling through motivational interviewing, home-based physiotherapy and four months of fitness training. The control group continued regular paediatric physiotherapy. Main measures: Outcomes included social participation in domestic life, social participation in recreation and leisure (Life-Habits for Children questionnaire and Children's Assessment of Participation and Enjoyment questionnaire), self-perception (Harter's Self-Perception Profile for Children) and parent-reported quality of life (Cerebral Palsy Quality of Life Questionnaire). Assessments were performed at baseline, at six months (except quality of life) and at twelve months. Results: Intervention resulted in a positive effect on social participation in domestic life at twelve months (mean between-group difference = 0.9, 95% confidence interval (CI) = 0.1 to 1.7 [1-10 scale], P = 0.03), but not at six months. No significant effects were found for social participation in recreation and leisure, self-perception at six months and twelve months or for quality of life at twelve months. Conclusions: The combination of counselling, home-based physiotherapy and fitness training was not effective in improving social participation in recreation and leisure, self-perception or quality of life, but did show a potential for improving social participation in domestic life over the longer term.