A longitudinal field experiment examined a leader self-regulation intervention in teams engaged in a Business Strategy Module (BSM) of a University course. The BSM which is an integral part of the degree programme involved teams of four or five individuals under the direction of a leader working on a (simulated) car manufacturing task over a period of 24 weeks. Various aspects of team performance contributed towards module assessment. All leaders received multi-source feedback of leader task-relevant capabilities (fromthe leader followers andmodule tutor). Leaders were randomly allocated into a self-regulation intervention (15 leaders 46 followers) or control (25 leaders 109 followers) conditions. The intervention which was run by an independent coach was designed to improve leaders' use of self-regulatory processes to aid the development of task-relevant leadership competencies. Survey data was collected from the leaders and followers (on three occasions: pre- and two post-test intervention) team financial performance (three occasions: post-test) and a final teamreport (post-test). The leader self-regulation intervention led to increased followers' ratings of leader's effectiveness higher team financial performance and higher final team grade compared to the control (non-intervention) condition. Furthermore the benefits of the self-regulation intervention were mediated by leaders' attaining task-relevant competencies.