Negativity bias, the cognitive tendency to prioritize negative stimuli, is commonly observed in anxiety disorders and contributes to emotional and cognitive dysregulation. This study investigated the associations between conscious negativity bias, brain function, reported symptoms, and cognitive performance in 1990 patients with anxiety disorders. We hypothesized that greater negativity bias would be linked to altered brain function in regions involved in cognitive control and attention, deficits in memory, stress and anxiety control, resilience, and symptoms of negative affect and emotional instability. Voxel-based analysis of single photon emission computed tomography (SPECT) scans revealed significant hypoperfusion in the frontal, temporal, and parietal lobes, regions critical for cognitive control and emotional regulation. Increased perfusion in cerebellar lobules IV–VI, associated with somatomotor and emotional processing, was also observed. These neural patterns were strongly aligned with patient-reported symptoms, including elevated anxiety, depression, intrusive thoughts, decreased motivation, and suicidal ideation. In addition, cognitive assessments from the total brain platform showed that higher negativity bias was linked to deficits in emotional regulation, memory, stress and anxiety control, and resilience. These findings suggest that negativity bias contributes to widespread brain dysfunction, exacerbating emotional instability, and cognitive control deficits in patients with anxiety disorders. This study highlights the importance of targeting negativity bias in therapeutic interventions to improve emotional and cognitive outcomes. Future research should investigate the neural mechanisms linking negativity bias to mental health outcomes.