BACKGROUND: Although comorbid anxiety disorders are common in children with bipolar disorder (BD), it is unclear how this comorbidity impacts the pathophysiology of the illness. METHODS: Pediatric BD with lifetime anxiety (BD+ANX, n = 20), BD without lifetime anxiety (BD-ANX, n = 11), and controls (n = 14) were administered the visual-probe paradigm, which assesses attention bias to threat faces. RESULTS: Bipolar disorder +ANX demonstrated a stronger bias toward threat relative to BD-ANX and controls; the latter two did not differ from each other. CONCLUSIONS: Bipolar disorder +ANX showed a bias toward threat while, in two previous studies, anxious children showed a bias away from threat faces. Future studies should compare the pathophysiology of BD with and without a comorbid anxiety disorder and anxiety disorders presenting alone.