This study investigated the effects of training in cooperative skills in handbell performance for a child with intellectual disability and autism spectrum disorder. We implemented three tasks,“harmony tone,” “call and response,” and “musical scale.” For each task, five target behaviors were designated, including “synchronizing timing to ring handbells,” “coordinating progress in ringing handbells,” “observing the preceding person’s bell and ringing the handbell accordingly,” “making eye contact with the sub-trainer,” and “moving the body in harmony with the melody and others.” During the intervention phase, we changed the seating arrangement for the “harmony tone” and “call and response” tasks from side by side to facing each other. Additionally, we introduced reinforcement procedures only for the “harmony tone” task. The main trainer presented a whiteboard with written target behaviors and promptly rewarded the participant by placing character stickers on it that the child liked, whenever a target behavior occurred. As a result, the number of correct responses for each target behavior increased during the intervention phase over the baseline. Furthermore, generalization to untrained rhythms and other aspects was observed. Based on these results, we discuss the factors related to the acquisition and execution of cooperative skills.