Despite high levels of exposure, firefighter posttraumatic stress disorder (PTSD) rates are unclear. Likewise, questions remain regarding how social interactions and beliefs about emotion might interact to influence PTSD in firefighters. In this study, U.S. urban firefighters (N = 225) completed measures of social support, negative social interactions, and fear of emotion which were then used via regression analyses to predict PTSD symptoms. Each independent variable predicted PTSD beyond variance accounted for by demographic variables. Additionally, fear of emotion emerged as the strongest individual predictor of PTSD and a moderator of the relation between social interactions and PTSD symptoms. These findings emphasize the importance of beliefs about emotion; both in how these beliefs might influence the expression of PTSD symptoms, and in how the social networks of trauma survivors might buffer distress.