Purpose. This case study quantified kinematic and kinetic effects of gastrocnemius lengthening on gait in a Cerebral Palsy child with equinus foot. Methods. A 10-year-old diplegic child with Cerebral Palsy was evaluated with Gait Analysis (GA) before and after gastrocnemius fascia lengthening, investigating the lower limb joints kinematics and kinetics. Results. Kinematics improved at the level of distal joints, which are directly associated to gastrocnemius, and also at the proximal joint (like hip); improvements were found in ankle kinetics, too. Conclusions. This case study highlighted that GA was effective not only to quantify the results of the treatment but also to help preoperative decision making in dealing with CP child.