["Journal of Organizational Behavior, EarlyView. ", "\nABSTRACT\nEvidence of the beneficial impacts of servant leadership, which prioritizes the fulfillment of followers' needs, abounds. However, we lack knowledge about how organizations can foster leaders to engage in servant leadership and cultivate its benefits. In this research, we examine how the functional theory of counterfactual thinking (FTCT), which highlights the positive implications of reflecting on alternative courses of action that could have been taken, informs an intervention approach to developing servant leadership. We contend that a leader's engagement in servant leadership toward a follower can be facilitated by having the leader participate in a counterfactual thinking intervention that encourages them to think about how they could have behaved differently to better serve the follower's needs in their past interactions. We term this intervention the counterfactual thinking intervention for servant leadership (CTISL). We also propose that the positive effects of CTISL on the leader's servant leadership extend to the follower's thriving and serving behaviors. To test these contentions, we conducted two pretest‐posttest randomized experiments. In Study 1, we examined the effectiveness of the intervention and its effect on the leader's servant leadership intentions using a sample recruited via Prolific. In Study 2, we conducted a field experiment with a sample drawn from multiple organizations to examine the effects of the intervention on the leader's servant leadership and, in turn, on the follower's thriving and serving behaviors. The results supported our hypotheses. We advance the understanding of servant leadership development by demonstrating how insights from FTCT can be leveraged in organizational settings to cultivate servant leadership and its beneficial outcomes.\n"]