Physical activity is associated with better health in individuals with cerebral palsy (CP). Numerous physical activity interventions have been designed to promote physical activity among youth with CP. No previous studies have explored the factors contributing to the intention to participate and predicting attendance behaviour for these interventions. Using theory of planned behaviour (TPB), this study explored the prediction of physical activity intention and attendance behaviour in a physical activity intervention aiming to promote physical activity in a sample of young individuals with CP. Males with CP aged 9-21 years were asked to complete measures of attitude, subjective norms, perceived behavioural control and, intentions towards a physical activity intervention. Participants had no cognitive impairments to understand and follow instructions, were categorised into Gross Motor Function Classification System I-III, did not receive any specific lower limbs' medical treatment, or did not participate in a strength training program for lower limbs within 6 months before the study. Subjective norms were found to be the only significant predictor of intention, accounting for 83% of variance in intention. Intention and perceived behaviour control were found to be a nonsignificant predictor of attendance behaviour in youth with CP. The results show that TPB is a relevant tool in the prediction of intention towards a physical activity intervention in Finnish youth with CP.