Firefighters are exposed to potentially traumatic events throughout their careers, placing them at heightened risk for the development of posttraumatic stress disorder (PTSD). Individuals experiencing PTSD symptoms often experience interpersonal problems and relationship stress, and this may be due to emotion regulation difficulties. The current study examined the association between PTSD symptoms, couple relationship satisfaction, and emotion regulation difficulties among firefighters. Participants were comprised of 188 firefighters ( M age = 41.32, SD = 9.25, 97.3% male) who completed an online questionnaire. Results indicated that PTSD symptom severity was negatively associated with relationship satisfaction and positively associated with emotion regulation difficulties. Additionally, there was a significant negative indirect effect of PTSD symptom severity on relationship satisfaction through heightened emotion regulation difficulties. Negative alterations in cognition and mood were especially relevant to emotion regulation difficulties and relationship satisfaction. Findings highlight the importance of understanding associations between PTSD and interpersonal functioning among firefighters. Emotion regulation difficulties may offer a clinically relevant transdiagnostic factor for targeting PTSD symptoms and relationship functioning among firefighters.