Sibling relationships are important in human life, and in cases of typically developing siblings of children with Autism Spectrum Disorder (ASD), this relationship has been the subject of scientific research, especially in recent years. The aim of this study was to investigate the effect that a child with Autism Spectrum Disorder (ASD) has on his or her sibling in relation to the levels of social anxiety experienced. The research hypotheses were formulated as follows: 1. The level of anxiety differs between siblings of children with ASD and siblings of typically developing children, and 2. Siblings of children with ASD avoid social situations more often than siblings of typically developing children because they experience anxiety related to these situations. The research sample consisted of 60 siblings of children with ASD and 60 siblings of typically developing children who were enrolled in one of the educational levels from kindergarten to high school. Social anxiety was assessed with a questionnaire that included the Social Anxiety Scale for Children-Revised as well as questions about the demographic characteristics of the sample (e.g., gender, age, birth order, place of residence, etc.). The results of the study showed that siblings of children with ASD experience more difficulties in social situations compared to siblings of typically developing children. The findings of the study are discussed in the context of the importance of the services provided by specialists, which aim to design, implement, and evaluate appropriate interventions for siblings of children with ASD and other family members.