The assessment of oppositional defiant disorder, conduct disorder, antisocial personality disorder, and intermittent explosive disorder—the Disruptive, Impulse Control and Conduct Disorders—can be affected by biases in clinical judgment, including overestimating concerns about distinguishing symptoms from normative behavior and stigma associated with diagnosing antisocial behavior. Recent nosological changes call for special attention during assessment to symptom dimensions of limited prosocial emotions and chronic irritability. The present review summarizes best practices for evidence-based assessment of these disorders and discusses tools to identify their symptoms. Despite the focus on disruptive behavior disorders, their high degree of overlap with disruptive mood dysregulation disorder can complicate assessment. Thus, the latter disorder is also included for discussion here. Good practice in the assessment of disruptive behavior disorders involves using several means of information gathering (e.g., clinical interview, standardized rating scales or checklists), ideally via multiple informants (e.g., parent-, teacher-, and self-report). A commitment to providing a full and accurate diagnostic assessment, with careful and attentive reference to diagnostic guidelines, will mitigate concerns regarding biases.