BackgroundAnxiety disorders are highly prevalent and debilitating conditions that show high comorbidity rates in adolescence. The present article illustrates how Unified Protocol for Transdiagnostic Treatment of Emotional Disorders in Adolescents (UP-A) was adapted for Iranian adolescents with anxiety disorders.MethodsA total of 54 adolescents with comorbid anxiety disorders participated in a randomized, waitlist-controlled trial of group weekly sessions of either UP-A or waitlist control (WLC). Primary and process of change outcomes were assessed at baseline, posttreatment, and 1-month follow-up.ResultsSignificant changes were observed over time on major DSM-5 anxiety disorder symptoms (F(2, 51) = 117.09, p < 0.001), phobia type symptoms (F(2, 51) = 100.67, p < 0.001), and overall anxiety symptoms (F(2, 51) = 196.29, p < 0.001), as well as on emotion regulation strategies of reappraisal (F(2, 51) = 17.03, p < 0.001), and suppression (F(2, 51) = 21.13, p < 0.001), as well as on intolerance of uncertainty dimensions including prospective (F(2, 51) = 74.49, p < 0.001), inhibitory (F(2, 51) = 45.94, p < 0.001), and total intolerance of uncertainty (F(2, 51) = 84.42, p < 0.001), in favor of UP-A over WLC.ConclusionOverall, results provide a cultural application of the UP-A and support the protocol as useful for improving anxiety disorders as well as modifying of emotion regulation strategies and intolerance of uncertainty dimensions in Iranian adolescents. Future directions and study limitations are discussed.