Background: Executive control deficits are common sequelae of childhood traumatic brain injury (TBI). The goal of the current study was to assess a specific executive control function, performance monitoring, in children following TBI. Methods: Thirty-one children with mild-moderate TBI, 18 with severe TBI, and 37 control children without TBI, of comparable age and sex, performed the stop signal task, a speeded choice reaction time task. On occasion, they were presented with a signal to stop their responses. Performance monitoring was defined as the extent of slowing in go-task reaction time following failure to stop responses. Results: The TBI group as a whole demonstrated less post-error slowing than did controls. This finding suggested impaired error monitoring performance. In addition, time since injury and socioeconomic status predicted less slowing after stopped responses. Conclusions: We suggest that alterations in performance monitoring expressed as the inability to notice, regulate and adjust behavior to changing situations are an effect of TBI in children.