Previous research has established the link between posttraumatic stress disorder (PTSD) and suicidal behavior. In the current study, constructs proposed to explain this relationship were examined, applying the framework of the interpersonal-psychological theory of suicide (IPTS). Relationships between acquired capability for suicide (ACS; i.e., fearlessness about death [FAD] and pain tolerance) and specific PTSD symptom clusters were explored. In a sample of 334 trauma-exposed undergraduates, anxious arousal and FAD were negatively associated, and numbing and pain tolerance were positively associated. Results establish a foundation for investigating the role of ACS in understanding observed relationships between suicidal behavior and PTSD symptoms.