In this systematic review, we aimed to identify the impact of the COVID-19 pandemic on children/adolescents with a diagnosis of autism spectrum disorder (ASD). The protocol was registered on PROSPERO CRD42021255848. Articles were selected from PubMed, Embase, and LILACS according to these characteristics: patients from zero to 18 years old, exposed to the COVID-19 pandemic, impact on social communication/interaction and restricted/repetitive behavior domains. The Newcastle-Ottawa Scale was used to assess methodological quality and the risk of bias. Of the 351 articles initially identified, 26 were finally included with information on 8,610 patients. Although the studies were heterogeneous, they indicated that the pandemic-related issues experienced by patients with ASD were mostly manifested in their behavior and sleep patterns.