Alcohol use problems are associated with suicidal desire and may provide an avenue to suicidal ideation and behavior. However, the influence of posttraumatic stress disorder (PTSD) on the nature of the relationship between alcohol use problems and suicide risk is not well understood. In particular, the potential for PTSD to moderate the association between alcohol use problems and suicide risk remains unexplored. The present study investigated the main and interactive effects of alcohol use problems (Alcohol Use Disorders Identification Test) and PTSD symptoms (PTSD Checklist for DSM-5) on suicide risk (Suicide Behaviors Questionnaire-Revised) in a sample of 632 trauma-exposed firefighters (93.5% men; Mage = 38.44 years, SD = 8.59). Hierarchical logistic regression analyses evaluated whether the main and interactive effects of PTSD symptom severity and alcohol use disorders were significantly related to suicide risk, above and beyond age and cumulative trauma. The main effects of PTSD symptom severity (odds ratio, 1.76; p < 0.001) and alcohol use problems (odds ratio, 1.37; p = 0.391) significantly positively predicted suicide risk; however, PTSD symptoms did not moderate an association between alcohol use problems and suicide risk after accounting for these main effects (p > 0.05). A secondary, exploratory aim demonstrated that all PTSD symptom clusters significantly positively predicted suicide risk (p's < 0.001), although none of these clusters interacted with alcohol use problems to predict suicide risk (p's > 0.05). Theoretical and clinical implications are discussed as they relate to the importance of screening for PTSD and alcohol use disorder among firefighter populations.