OBJECTIVE: To evaluate the efficacy, safety, and tolerability of the selective serotonin norepinephrine inhibitor duloxetine in children and adolescents with generalized anxiety disorder (GAD). METHOD: Youth aged 7 through 17 years with a primary diagnosis of GAD were treated with flexibly dosed duloxetine (30-120 mg daily, n = 135) or placebo (n = 137) for 10 weeks, followed by open-label duloxetine (30-120mg daily) for 18 weeks. Efficacy measures included the Pediatric Anxiety Rating Scale (PARS), Clinical Global Impression-Severity (CGI-Severity) scale, and Children's Global Assessment Scale (CGAS). Safety measures included the Columbia-Suicide Severity Rating Scale (C-SSRS) as well as vital signs and electrocardiographic and laboratory monitoring. RESULTS: On the primary efficacy measure (PARS severity for GAD), mean improvement from baseline to 10 weeks was statistically significantly greater for duloxetine (-9.7) compared with placebo (-7.1, p ≤ .001, Cohen's d: 0.5). Symptomatic response (50% improvement on the PARS severity for GAD), remission (PARS severity for GAD ≤8), and functional remission (CGAS >70) rates for the duloxetine group (59%, 50%, 37%, respectively) were statistically significantly greater than for the placebo group (42%, 34%, 24%, respectively, p ≤ .05) during acute treatment. Changes in systolic and diastolic blood pressure and discontinuation because of adverse events did not statistically differ between the duloxetine and placebo groups, although gastrointestinal-related adverse events, oropharyngeal pain, dizziness, cough, and palpitations were reported with a statistically significantly greater incidence for the duloxetine group compared with the placebo group. Mean changes in pulse and weight for the duloxetine group (+6.5 beats/min, -0.1 kg, respectively) were statistically different from the placebo group (+2.0 beats/min, +1.1 kg, respectively, p ≤ .01). CONCLUSION: In this study, duloxetine was superior to placebo on the primary efficacy analysis of mean change from baseline to week 10 on the PARS severity for GAD score, and safety results were consistent with the known safety profile of duloxetine in pediatric and adult patients. Clinical trial registration information-A Study in Pediatric Participants With Generalized Anxiety Disorder; http://clinicaltrials.gov; NCT01226511.