The purpose of the present study was to examine (a) the teacher-reported prevalence of attention-deficit/hyperactivity disorder (ADHD) symptoms and associated impairment in a nationally representative sample of children and adolescents and (b) the degree to which prevalence varied as a function of student and teacher characteristics. Teacher-reported symptoms of ADHD based on Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5) criteria and teacher-rated impairment were used to estimate prevalence using symptoms and impairment either alone or in combination, and to assess predictors of ADHD using a diverse, nationally representative sample (n = 2,140; 1,070 males, 1,070 females; 54.8% White, non-Hispanic) between 5 to 17 years old (M = 11.53; SD = 3.54). The combination of symptom and impairment ratings yielded the prevalence rate most consistent with prior epidemiological findings. Students' age, gender, racial, and special education status were significant predictors of symptom count and level of symptom-related impairment. It is critically important to simultaneously consider symptoms and symptom-related impairment when identifying students with ADHD. Student and teacher characteristics may affect ratings and identification results.