Group functional magnetic resonance imaging (fMRI) studies suggest that anxiety disorders are associated with anomalous brain activation and functional connectivity (FC). However, brain-based features sensitive enough to discriminate individual subjects with a specific anxiety disorder and that track symptom severity longitudinally, desirable qualities for putative disorder-specific biomarkers, remain to be identified. Blood oxygen level-dependent (BOLD) fMRI during emotional face perceptual tasks and a new, large-scale and condition-dependent FC and machine learning approach were used to identify features (pair-wise correlations) that discriminated patients with social anxiety disorder (SAD, N Ā¼ 16) from controls (N Ā¼ 19). We assessed whether these features discriminated SAD from panic disorder (PD, N Ā¼ 16), and SAD from controls in an independent replication sample that performed a similar task at baseline (N: SAD Ā¼ 15, controls Ā¼ 17) and following 8-weeks paroxetine treatment (N: SAD Ā¼ 12, untreated controls Ā¼ 7). High SAD vs HCs discrimination (area under the ROC curve, AUC, arithmetic mean of sensitivity and specificity) was achieved with two FC features during unattended neutral face perception (AUC Ā¼ 0.88, Po0.05 corrected). These features also discriminated SAD vs PD (AUC Ā¼ 0.82, P Ā¼ 0.0001) and SAD vs HCs in the independent replication sample (FC during unattended angry face perception, AUC Ā¼ 0.71, P Ā¼ 0.01). The most informative FC was left hippocampus-left temporal pole, which was reduced in both SAD samples (replication sample P Ā¼ 0.027), and this FC increased following the treatment (post4pre, t (11) Ā¼ 2.9, P Ā¼ 0.007). In conclusion, SAD is associated with reduced FC between left temporal pole and left hippocampus during face perception, and results suggest promise for emerging FC-based biomarkers for SAD diagnosis and treatment effects.