Cognitive, coping, and trauma symptom predictors of posttraumatic growth (PTG; measured with the Posttraumatic Growth Inventory) were examined in a large convenience sample (n =1505) participating in a longitudinal Internet-based study following the terrorist attacks of 9/11/01. Results indicate that initial PTG levels (mean 9 weeks post-attacks) were generally associated with higher trauma symptoms (measured with the PTSD Checklist - Specific), positive changes in worldview (measured with the Changes in Outlook Questionnaire), more denial, and less behavioral disengagement (measured with the Brief COPE). Additionally, PTG had a curvilinear association with level of trauma symptoms, such that those reporting symptoms at intermediate levels reported the highest levels of growth. Levels of PTG declined somewhat over time with the exception of Spiritual Change. As expected, PTG levels at follow-up (mean 6.5 months post-attacks) were primarily predicted by initial PTG levels; however, decreases from baseline in trauma symptoms and increases from baseline in positive worldview, acceptance, and positive reframing were also associated with higher reported posttraumatic growth at follow-up. These findings suggest that there may be a range of traumatic experience most conducive to growth and they also highlight the important contributions of cognitive and coping variables to psychological thriving in short- and longer-term periods following traumatic experience.