Relations between a modifiable psychosocial factor, self-efficacy (SE), and behavioral and neural indices of self-regulation, including post-error behavior, the error-related negativity (ERN), and error positivity (Pe) were examined in young adults during a flanker task emphasizing either accuracy or speed. SE was predicted to be associated with larger ERN and Pe amplitudes, as well as greater post-error behavioral performance during task conditions emphasizing accuracy, but not speed. Results showed that higher SE was associated with greater post-error response accuracy during the accuracy condition, but not the speed condition, and higher SE was related with greater ERN amplitudes across instruction conditions. Further, ERN amplitude mediated the relationship between SE and post-error response accuracy in the accuracy condition. These findings emphasize the role of motivation and incentive on the self-regulatory system and suggest that SE is beneficially related to self-regulatory processes and outcomes.