The coachee's self is central to coaching. Yet the roles that different self-related concepts play in coaching have been insufficiently studied. Specifically, self-control and self-regulation have been conflated or treated as identical concepts. Using the theory of personality systems interactions, we investigated how the development of self-management competencies (SMCs) within coaching facilitates coaching success in two studies with professional samples. Additionally, we examined how coaches support coachees' development of these competencies. Study 1 employed a longitudinal design. Caregivers working as managers engaged in a 5-month coaching programme. Goal attainment increased, need frustration decreased and the SMCs self-regulation and self-access increased, with self-regulation predicting coachees' goal attainment. In Study 2, we conceptually replicated the finding that self-regulation is positively related to coaching success. With a cross-sectional design, we matched self-reported data of 298 coachees with self-reported data of their 75 respective coaches. In a structural equation model, we found that a strong coaching relationship reported by the coaches positively related to the SMCs reported by the coachees. Self-regulation again showed the strongest effect on coaching success. These findings provide theoretical insights into the different effects of self-regulation and self-control on coaching effectiveness and suggest areas of focus for coaches.