Knowledge of attention deficit hyperactivity disorder (ADHD) and attitudes toward teaching children with ADHD are compared across stages of Australian teachers' careers. Relative to pre-service teachers with (n = 218) and without (n = 109) teaching experience, in-service teachers (n = 127) show more overall knowledge of ADHD, more knowledge of characteristics and treatments for ADHD, and higher perceived knowledge. In-service teachers reported less favorable emotion about teaching children with ADHD than did pre-service teachers without experience and more favorable behaviors than pre-service teachers with experience. Groups did not differ in knowledge of causes of ADHD, overall attitudes, stereotypical beliefs, and beliefs about teaching children with ADHD. Identification of knowledge gaps and ambivalent attitudes will guide pre-service and in-service training courses.