The current study examined prospective bidirectional links between dysregulated sleep, and anxiety and depression severity across 4years, among youth with a history of anxiety disorder. Participants were 319 youth (age 11-26years), who previously participated in a large multisite randomized controlled trial for the treatment of pediatric anxiety disorders, Child/Adolescent Anxiety Multimodal Study (CAMS), and subsequently enrolled in a naturalistic follow-up, Child/Adolescent Anxiety Multimodal Extended Long-term Study (CAMELS), an average of 6.5years later. They participated in four annual visits that included self-report items of dysregulated sleep and semi-structured multi-informant interviews of anxiety and depression. Dysregulated sleep was bidirectionally associated with clinician-rated anxiety and depression symptom severity across adolescence and young adulthood. However, these bidirectional relationships were attributable to youth mean levels of dysregulated sleep, and anxiety and depression severity over the 4 years. Elevations in dysregulated sleep at each visit, relative to mean levels, did not predict worse anxiety or depression severity 1 year later. Likewise visit-specific elevations in anxiety and depression severity, as opposed to average levels, did not predict higher levels of dysregulated sleep at the next visit. Having higher levels of dysregulated sleep or more severe internalizing problems across the four-year period, as opposed to reporting a relative increase in symptom severity at a particular visit, posed greater risk for poor mental health. Interventions should continue to assess and treat persistent sleep problems alongside anxiety and depression.