Objective: Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) A-criteria for ADHD were expanded to include new descriptors referencing adolescent and adult symptom manifestations. This study examines the effect of these changes on symptom endorsement in a sample of adolescents with ADHD (N = 259; age range = 10.72-16.70). Method: Parent ratings were collected and Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR) and DSM-5 endorsement of ADHD symptoms were compared. Results: Under the DSM-5, there were significant increases in reported inattention, but not hyperactivity/impulsivity (H/I) symptoms, with specific elevations for certain symptoms. The average adolescent met criteria for less than one additional symptom under the DSM-5, but the correlation between ADHD symptoms and impairment was attenuated when using the DSM-5 items. Impulsivity items appeared to represent adolescent deficits better than hyperactivity items. Results were not moderated by demographic factors. Conclusion: In a sample of adolescents with well-diagnosed DSM-IV-TR ADHD, developmental symptom descriptors led parents to endorse slightly more symptoms of inattention, but this elevation is unlikely to be clinically meaningful.