Social anxiety disorder (SAD) is characterized by negative self-beliefs and altered brain activation in the default-mode network (DMN). However, the extent to which there is neurocognitive heterogeneity in SAD remains unclear. We had two independent samples of patients perform a self-referential encoding task and complete self-reports of childhood maltreatment, subjective well-being, and emotion regulation. In the replication sample, we also measured DMN activation using functional MRI. We used k-means clustering, which revealed two distinct subgroups of patients with SAD in the discovery sample. Cluster 1 demonstrated higher levels of negative self-referential trait endorsement, lower levels of positive self-referential trait endorsement, and significantly higher levels of childhood emotional maltreatment, lower subjective well-being, and altered emotion-regulation-strategy use. A similar pattern was observed in the replication sample, which further demonstrated higher DMN activation during negative trait judgments in Cluster 1. Participants in the SAD clusters, from both the discovery and replication samples, were significantly distinct from samples of control participants. These findings reveal neurocognitive heterogeneity in SAD and its relationship to emotional maltreatment.