Refugees are highly vulnerable to mental health disorders and head injuries. The primary aim of this study is to examine the impact of posttraumatic stress disorder (PTSD) and head injury on reactive and appetitive aggression in adult Syrian refugees in Lebanon. A cross-sectional study was conducted targeting adult Arab United Nations High Commissioner for Refugees-registered Syrian refugees residing in Beirut and southern regions of Lebanon. Eligible refugees completed a battery of questionnaires including the PTSD Checklist for Diagnostic and Statistical Manual of Mental Disorders, fifth edition, the Trauma Events and Head Injury sections of the Harvard Trauma Questionnaire, the Buss-Perry Aggression Questionnaire, and the Appetitive Aggression Scale. A total of 191 Syrian refugees participated in the study: 62.83% were females, and the mean age was 31.01 years (SD = 10.98). The severity of PTSD (adjusted B = 0.18, 95% CI [0.05, 0.31], p = .006), having experienced at least one head injury trauma event (adjusted B = 10.20, 95% CI [1.61, 18.79], p = .020), and the severity of somatic symptoms (adjusted B = 0.71, 95% CI [0.23, 1.20], p = .004) were significant risk factors of reactive aggression. As for appetitive aggression, males (females adjusted OR [aOR] = 0.06, 95% CI [0.02, 0.18], p < .001), younger individuals (aOR = 0.95, 95% CI [0.91, 0.99], p = .024), and higher severity of somatic symptoms (aOR = 1.20, 95% CI [1.09, 1.32], p < .001) were significant risk factors. PTSD and head injury are independent risk factors for reactive aggression but not appetitive aggression in Syrian refugees in Lebanon, while the severity of somatic symptoms is an independent risk factor for both reactive and appetitive aggression. (PsycInfo Database Record (c) 2024 APA, all rights reserved).