The aim was to evaluate the efficacy of venlafaxine extended release (ER) on characteristics of resilience, measured by the Connor-Davidson Resilience Scale, in patients with posttraumatic stress disorder (PTSD). Data were evaluated from a randomized, 6-month, international, multicenter study of adult outpatients with a primary diagnosis of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition PTSD for ≥6 months, and 17-item Clinician-Administered PTSD Scale score ≥60. Patients were assigned randomly to treatment with flexible-dose venlafaxine ER (37.5-300 mg/day) or placebo. Changes from baseline scores and effect sizes of response to treatment with venlafaxine ER compared with placebo were computed for each item, as well as for the newly developed 2-item and 10-item subscales. Effect sizes across items ranged from 0.41 (moderate) to 0.08 (very weak). The effect size for the Resilience Scale-2 (2-item subscale) was 0.32, which was comparable to the effect sizes of 0.35 for the 25-item full scale and 0.34 for the 10-item subscale. Venlafaxine ER improved resilience on individual Connor-Davidson Resilience Scale items that reflect four factors (hardiness, persistence/tenacity, social support, and faith in a benevolent or meaningful world), to varying degrees in patients with PTSD. The findings suggest that assessment of treatment response might be enhanced by routine evaluation of resilience.