This article offers a conceptual and developmental proposition based on the centrality of the practitioner’s self in the achievement of coaching outcomes. The central role of the self of the coach is established through a theoretical comparison with a competency (knowledge and skills) frame. Positioning the self in this way acknowledges the complexity and unpredictability of the coaching process and aligns with a complex-adaptive-system perspective on coaching. In turn, it provides a platform for a professional-practice view of the self as the main instrument of coaching and, further, a developmental proposition for the good use of self as an instrument. Three main conditions for the good use of self as an instrument are proposed: understanding the instrument, looking after the instrument, and checking the instrument for quality and sensitivity. Each condition is discussed, and the implications for coaches and educators of coaching in relation to initial training and the continuing professional development of coaches are considered. In keeping with the underpinning theory of self around which it is built, this article gives witness to multiple voices: theory, practice, and development.