Functional communication training (FCT) is an evidence-based practice used to mitigate challenging behavior by increasing functional communication skills. To increase the practicality and feasibility of FCT in natural settings, thinning schedules of reinforcement are typically programmed following FCT. In this review, we meta-analyzed 28 studies that incorporated a thinning schedule procedure following FCT for 51 children with intellectual and developmental disabilities ages 8 and younger. Using Tau-U, the results demonstrated overall moderate effect sizes for both challenging behavior and functional communication responses. Additionally, moderator analyses pertaining to participant characteristics, interventions, and study quality were conducted. Thinning procedures were most effective for children who had stronger communication repertoire. Implications for future research and practice are discussed.