Aim: To determine the neuromuscular outcomes of an eccentric strength-training programme for children and adolescents with cerebral palsy (CP). Method: In this randomised, parallel-group trial with waiting control, 14 participants with CP (six males, eight females; mean age 11y, SD 2y range 9-15y), diagnosed with upper-limb spasticity were compared with 14 age- and sex-matched typically developing participants. Participants with CP completed a 6-week progressive resistance-strengthening programme, performing eccentric lengthening contractions of their upper limb three times a week. Data from dynamometer and surface electromyography (EMG) assessments included peak torque normalised to body mass (T/Bm), work normalised to body mass (W/Bm), angle at peak torque, curve width, and EMG activation. Results: After training, children with CP had improved eccentric T/Bm (p = 0.009) and W/Bm (p = 0.009) to a level similar to that of the typically developing children. No change in angle of peak torque occurred, although curve width increased both concentrically (p = 0.018) and eccentrically (p = 0.015). EMG activity was elevated before training in children with CP but decreased with training to levels similar to those of the typically developing children. Interpretation: With eccentric strength training, children with CP increased torque throughout range of motion. Results suggest that eccentric exercises may decrease co-contraction, improving net torque development. Eccentric actions may be important in the maintenance of the torque-angle relationship. These results have significant implications for the prescription of strength-training programmes for people with CP.