Previous research has suggested there may be racial differences in how adults perceive and rate children’s ADHD behavior (i.e., inattention, hyperactivity, impulsivity). The current study examined these differences between African-American/Black (AA/B) parents and European-American/White (EA/W) parents and teachers. Participants watched video clips of children in classrooms and rated their ADHD behaviors and their likelihood of having ADHD. Results showed that EA/W parents and teachers rated African-American boys’ ADHD behaviors and their likelihood of having ADHD higher than AA/B parents. Mechanisms by which these differences exist were explored, including beliefs about stigma related to ADHD, values in movement and expressiveness, experiences with racism, and racial attitudes. Results suggested that EA/W teachers’ racial attitudes toward African Americans were related to their ratings of African-American boys’ ADHD behaviors and likelihood of having ADHD. More research is necessary to further explain the mechanisms by which such discrepancies in ratings of African-American boys’ ADHD behaviors exist between African-American and European-American adults to inform culturally sensitive assessment and diagnosis of ADHD in African-American children.