Insecure adult attachment dimensions are consistently related to poorer posttrauma adjustment, but these relations have rarely been examined prospectively or across a wide range of potentially traumatic events. In addition, the factors mediating these relations are not yet fully understood. Therefore, the first aim of this study was to assess whether anxious and avoidant attachment dimensions assessed preevent would predict changes in adjustment (e.g., distress) following a broad range of potentially traumatic events. The second aim was to determine whether postevent social resources mediated the relations between attachment dimensions and postevent adjustment. Undergraduate students (N = 1,084) completed preevent measures of attachment dimensions and psychological distress at Time 1 (T1); 73% (n = 789) completed a follow-up survey 2 months later assessing exposure to potentially traumatic events and social resources (Time 2; T2). Those who reported experiencing a potentially traumatic event between T1 and T2 and who completed a final follow-up survey assessing distress 2 months after T2 (Time 3) constituted the sample for the present analyses (n = 174). Individuals with more attachment avoidance and anxiety had greater increases in posttraumatic stress disorder symptoms and general psychological distress. These relations were mediated by social resources (i.e., positive and negative support, social withdrawal) at T2 such that anxious and avoidant attachment dimensions were associated with having fewer social resources following a potentially traumatic event, which in turn was associated with reporting more distress. Implications for research and practice with individuals exposed to potentially traumatic events are discussed.