Uncivil behavior in the classroom is a growing issue among children and youth both academically and developmentally. This unique low-level antisocial behavior may be a precursor to higher-level antisocial behavior, and it is therefore important to have a relevant tool to be able to measure engagement in such behavior in the classroom. Using data from 586 children and youth (46.4% boys) between the ages of 10 and 14 (M = 12.02; SD = 1.35), we conducted a confirmatory factor analysis to validate a scale of classroom incivility consisting of two subscales based on intentionality (intentional and unintentional). We also ensured construct validity of our subscales by exploring HEXACO personality profiles and correlating our measures with both self- and peer-reported variables related to social and mental well-being. Our results highlight that engaging in classroom incivility is positively associated with poorer well-being, antisocial traits and antisocial behavior. Our results also demonstrate distinct personality profiles of students who reported engaging in intentional versus unintentional classroom incivility. This study is an important first step for future research exploring the potential antecedents and implications of engaging in uncivil behavior in the classroom, particularly if such behavior may have potential to escalate into more serious behavior later on.