This randomized controlled trial (RCT) aimed to pilot the newly developed manualized and monitored systemic therapy (ST) for social anxiety disorder (SAD), as compared to manualized and monitored cognitive behavioral therapy (CBT). We conducted a prospective multicenter, assessor-blind pilot RCT on 38 outpatients (ICD F40.1; Structured Clinical Interview for DSM (SCID); Liebowitz Social Anxiety Scale, LSAS-SR >30). The primary outcome was level of social anxiety (LSAS-SR) at the end of treatment. A total of 252 persons were screened, and 38 patients were randomized and started therapy (CBT: 20 patients; ST: 18 patients; age: M = 36 years, SD = 14). Within-group, simple-effect intent-to-treat analyses (ITT) showed significant reduction in LSAS-SR (CBT: d = 1.04; ST: d = 1.67), while ITT mixed-design ANOVA demonstrated the advantage of ST (d = 0.81). Per-protocol analyses supported these results. Remission based on reliable change indices also demonstrated significant difference (LSAS-SR: 15% in CBT; 39% in ST; h: 0.550), supported by blind diagnosticians' ratings of those who completed therapy (SCID; 45% in CBT, 78% in ST, p = .083). No adverse events were reported. CBT and ST both reduced social anxiety, supporting