The results from coaching research suggest that coaching offers a number of positive benefits including having a positive impact upon leadership. This chapter begins by reviewing the broader landscape of coaching research. It then explores the specific research underpinning a range of “key” factors relating to coaching including the coach, client, organizational clients, and the relationship between the coach and the client. The chapter provides a brief description on: the development of coaching research; coach factors; coachee factors; coach–coachee relationship factors; tripartite relationship and client factors; the role of coaching supervision; and methodological approaches in coaching. Executive coaching is frequently used by corporations to help executives develop their capacity to deal with change and to give them support in reaching their organizational or work-related goals. A key focus within the coaching psychology literature has been on understanding what factors and attributes differentiate the most successful coaches.