This study aimed to determine the effect of internalized stigma on peer relationships in adolescents with attention-deficit/hyperactivity disorder (ADHD). The study was conducted in a Special Education and Rehabilitation Center between August and September 2022. The correlational and cross-sectional study sample consisted of 70 adolescents with ADHD. The Descriptive Characteristics Form, the Internalized Stigma Scale for Children and Adolescents, and the Peer Relationship Scale were used to collect the data. It was determined that the mean total score of internalized stigma levels of adolescents was 93.24 (16.16), and the mean total score of peer relationships was 53.78 (10.76). It was determined that there was a strong negative correlation between the total score of internalized stigma and peer relationships (r = − 0.748, p = 0.001). In addition, it was determined that internalized stigma predicted peer relationships by 55%. It can be said that internalized stigma and peer relationships of adolescents are moderate, and as adolescents' internalized stigma levels increased, their peer relationships decreased.