Self-efficacy (SE) is a modifiable psychosocial factor related to individuals’ beliefs in their capabilities to successfully complete courses of action and has been shown to be positively associated with task performance. The authors hypothesized that one means through which SE is related with improved performance is through enhanced task-relevant attentional control during task execution. To assess this hypothesis, we examined the relationships between SE and behavioral and neural indices of task performance and task-relevant attentional control for 76 young adults during the completion of a flanker task. Results showed that greater SE was associated with greater response accuracy and P3b amplitude across task conditions, and faster RT under more difficult task conditions. Additionally, P3b amplitude was found to mediate the relationship between SE and task performance in the difficult condition. These findings suggest that greater attentional allocation to task-relevant processes, including monitoring stimulus-response relationships and focusing attention on working memory operations, may help explain the association between SE and improved task performance.