COVID-19 causes not only severe respiratory symptoms, but also long-term sequelae, even if the acute-phase symptoms are minor. Neurological and neuropsychiatric symptoms are emerging as major long-term sequalae. In patients with pre-existing behavioral symptoms, such as individuals with autism spectrum disorders (ASD), the emergence of neuropsychiatric symptoms due to long COVID can be difficult to diagnose and manage. The study presents 3 cases where COVID-19 had significant effects on patients with ASD and the difficulty of managing long-COVID symptoms.