This review examines the prevalence, phenomenology, and treatment of anxiety in children and adolescents with autism spectrum disorders (ASD). The study found that anxiety is common in this population, with prevalence rates ranging from 11% to 84%. Anxiety disorders, such as simple phobias, generalized anxiety disorder, separation anxiety disorder, obsessive-compulsive disorder, and social phobia, are frequently observed. The assessment of anxiety in ASD should involve multiple informants and modalities due to the atypical presentation of anxiety symptoms in children with ASD. Despite preliminary evidence for the efficacy of some pharmacological and psychosocial interventions, there is a lack of well-controlled studies using well-characterized samples. The review highlights the need for further research to develop effective assessment and treatment approaches for anxiety in children and adolescents with ASD.This review examines the prevalence, phenomenology, and treatment of anxiety in children and adolescents with autism spectrum disorders (ASD). The study found that anxiety is common in this population, with prevalence rates ranging from 11% to 84%. Anxiety disorders, such as simple phobias, generalized anxiety disorder, separation anxiety disorder, obsessive-compulsive disorder, and social phobia, are frequently observed. The assessment of anxiety in ASD should involve multiple informants and modalities due to the atypical presentation of anxiety symptoms in children with ASD. Despite preliminary evidence for the efficacy of some pharmacological and psychosocial interventions, there is a lack of well-controlled studies using well-characterized samples. The review highlights the need for further research to develop effective assessment and treatment approaches for anxiety in children and adolescents with ASD.