Heightened rates of posttraumatic stress disorder (PTSD) symptoms and alcohol use have been documented among firefighters. Emotion regulation difficulties (ERD) are clinically relevant to both PTSD and alcohol use. Few studies have examined the role of ERD in the association of PTSD symptoms with alcohol use severity and alcohol use motives among firefighters. Thus, the present investigation examined the indirect effect of PTSD symptom severity on alcohol use severity and alcohol use motives through ERD. The sample was comprised of 685 firefighters (Mage = 38.65, SD = 8.57, 93.6% male) recruited from an urban fire department in the southern U.S. to complete an online survey. Indirect effects were calculated using 10,000 bootstrapped samples. Effects were examined after accounting for years of fire service, occupational stress, trauma load (i.e., number of traumatic event types experienced); in models evaluating alcohol use motives as outcomes, other alcohol use motives (i.e., alternate motives subscales) were included as additional covariates. First, ERD explained the association of PTSD symptom severity with alcohol use coping motives (β = .01, SE = .003, 95% CI [.004-.01]). Furthermore, ERD did not significantly account for the association of PTSD symptom severity with alcohol use severity (β = .02, SE = .01, 95% CI [-.004-.04]), alcohol use enhancement motives (β = -.003, SE = .002, 95%CI [-.007-.000]), alcohol use social motives (β = .004, SE = .002, 95% CI [-.000-.01]), or alcohol use conformity motives (β = -.002, SE = .002, 95% CI [-.006-.02]). Results demonstrated that, among firefighters, PTSD symptom severity is positively related to alcohol use coping motives through heightened ERD. Clinical implications and future directions are discussed.