The present investigation examined the incremental predictive validity of mindfulness-based processes, indexed by the Kentucky Inventory of Mindfulness Skills, in relation to posttraumatic stress symptom severity among individuals without any axis I psychopathology. Participants included 239 adults who endorsed exposure to traumatic life events. Results indicated that the Accepting without Judgment subscale was significantly incrementally associated with posttraumatic stress symptoms; effects were above and beyond the variance accounted for by negative affectivity and number of trauma types experienced. The Acting with Awareness subscale was incrementally associated with only posttraumatic stress-relevant re-experiencing symptoms; and no other mindfulness factors were related to the dependent measures. Findings are discussed in relation to extant empirical and theoretical work relevant to mindfulness and posttraumatic stress.