Although irritability, anger, and aggression are diagnostic symptoms of posttraumatic stress disorder (PTSD), their clinical significance and associations with psychopathology remain unclear. In a sample of community adults with probable PTSD (n = 151), we measured irritability, physical aggression, verbal aggression, anger, and hostility with the Brief Irritability Test and the Brief Aggression Questionnaire. Participants' psychopathology, including depression, attention deficit and hyperactivity disorder (ADHD), psychotic-like experiences, insomnia, as well as suicidal behaviors were also assessed. Correlation analysis showed that irritability and anger were modestly related to all PTSD dimensions; physical aggression was related to avoidance, negative alterations in cognitions and mood (NACM), and hyperarousal; hostility was related to reexperiencing, NACM, and hyperarousal; while verbal aggression was not significantly related to any PTSD dimensions. After adjustment for trauma exposure and PTSD symptoms, irritability was associated with almost all psychopathology and suicidal behaviors, however, anger, hostility, and aggression were sparsely related to some psychopathology or suicidal behaviors. Particularly, anger was only related to ADHD and insomnia. Latent profile analysis based on PTSD, irritability, anger, hostility, and aggression indicated two discrete subgroups: the high severity group (33.8%) and the low severity group (66.2%), with high severity group reporting higher rates of comorbidity and suicidal behaviors. The findings support irritability, aggression, anger, and hostility as separate constructs; moreover, irritability, anger, and aggression should be independently measured in PTSD. Our findings also suggest the significance of irritability as a separate hallmark of PTSD and the need to incorporate PTSD dimensions. (PsycInfo Database Record (c) 2023 APA, all rights reserved).