Research indicates that negative affect (NA) is significantly associated with posttraumatic stress symptom severity (PTSS) (Tull, Jakupcak, McFadden, & Roemer, 2007). To further understand the relationship between NA and PTSS, thought suppression (TS) may be a mediator in this relationship. A mediation analysis was conducted in a sample of 105 college students who have endorsed a past experience of criterion A traumatic event. TS was found to partially mediate the relationship between NA and PTSS.