Individuals with Social Anxiety Disorder (SAD) are at risk for employment problems. This multi-site trial examined the efficacy of Work-Related Cognitive Behavioral Therapy provided alongside vocational services as usual (WCBT+VSAU), a group-based treatment designed to improve mental health and employment outcomes for individuals with SAD. Vocational service-seeking participants with SAD (N = 250) were randomized to either WCBT+VSAU or VSAU-alone. Hypotheses were that participants randomized to WCBT+VSAU would report less social anxiety, less depression, and more hours worked than participants randomized to VSAU-alone. WCBT+VSAU participants had significantly greater improvements on the Liebowitz Social Anxiety Scale (LSAS; d=−.25, CI=−0.49 to −0.02, p = .03) at post-assessment compared to VSAU-alone. The conditions did not differ on any variable at later time points or on secondary outcomes. Unexpectedly, participants randomized to VSAU-alone experienced LSAS improvements, similar to WCBT+VASU at later timepoints. Baseline psychological flexibility (beta=−.098 [−0.19–0.008]) and depression (beta=−0.18 [−0.34–0.009]) moderated change in social anxiety. Participants with lower psychological flexibility and higher depression responded more strongly to WCBT+VSAU than VSAU-alone over the duration of the study, suggesting that WCBT+VSAU may particularly benefit those with greater psychopathology. Results indicate that vocational centers are promising settings for treating SAD and employment-focused refinements are likely needed to improve work outcomes.