Attention-deficit/hyperactivity disorder (ADHD) and anxiety disorders are among the most common psychological problems in adolescence. It is not surprising that a large number of teens experience both ADHD and anxiety together. In fact, 1 in 4 teenagers with ADHD also has a co-occurring or “comorbid” anxiety disorder. While comorbidity rates vary depending on the population, the rates are estimated between 20% and 50% in epidemiological and clinical samples (Sciberras E et al., Pediatrics 133(5):801–808, 2014; Hammerness P et al., Eur Child Adolesc Psychiatry 19(2):107–112, 2010). These rates confirm that adolescents with ADHD are at a higher risk for developing an anxiety disorder than those without ADHD. This chapter will explore the etiology, clinical presentation, assessment, and treatment of anxiety disorders in teens with ADHD. We will discuss recent advances in our understanding of comorbid anxiety in this population and the unique challenges involved in treating both disorders. This will include some practical tips for parents, educators, and clinicians. Treatment will cover psychotherapeutic, medication, and school-based interventions.