Choices and response times in two-alternative decision-making tasks can be modeled by assuming that individuals steadily accrue evidence in favor of each alternative until a response boundary for one of them is crossed, at which point that alternative is chosen. Prior studies have reported that evidence accumulation during decision-making tasks takes longer in adults with psychopathology than in healthy controls, indicating that slow evidence accumulation may be transdiagnostic. However, few studies have examined perceptual decision making in anxiety disorders, where hypervigilance might enhance performance. Therefore, this study used the Hierarchical Drift Diffusion model to investigate evidence accumulation in adults with social anxiety disorder (SAD) and healthy controls as they performed a probabilistic reward task (PRT), in which social rewards were delivered for correct perceptual judgments. Adults with SAD completed the PRT before and after gaze-contingent music reward therapy (GCMRT), which trains attention allocation and has shown efficacy for SAD. Healthy controls also completed the PRT twice. Results revealed excellent performance in adults with SAD, especially after GCMRT: relative to controls, they showed faster evidence accumulation, better discriminability, and earned more rewards. These data highlight a positive effect of attention training on performance in anxious adults and show how a behavioral trait that is typically problematic-hypervigilance in SAD-can nevertheless confer advantages in certain contexts. The data also indicate that, in contrast to other forms of psychopathology, SAD is not characterized by slow evidence accumulation, at least in the context of the social PRT.