Coaching is defined as a one-to-one relationship in which the coach and coachee work together to identify and achieve organisationally, professionally, and personally beneficial developmental goals. However, it is often unclear what the relative effects of coaching are on specific coaching outcomes. We adopt meta-analytic techniques to investigate the predictive power of coaching on coach–coachee relationship outcomes, and coachee goal-attainment outcomes. Our findings suggest that coaching has stronger effects on eliciting relationship outcomes with the coachee than goal-attainment outcomes. Moreover, of the goal-attainment outcomes, coaching has the strongest effect on behavioural changes as opposed to attitudinal changes. Sample type, study design, background of the coach, and number of coaching sessions all emerged as significant moderators. Implications of these findings are discussed.