What is spirituality? What is leadership? And what is their relationship? The article presents the concept of "discernment" (Latin: "discretion") as the link ("tertium comperationis") between spirituality and leadership. Spirituality is a way of life in (the growth of) discernment towards human fullness, which is grounded in a moral universe (God, nature). Three elements are employed in discernment: spiritual traits (Cloninger), spiritual capital (Bourdieu) and spiritual transformation (Waaijman). The influence of spirituality on leadership is empirically tested in research among 97 leaders (principals) of Catholic schools in the Netherlands. The findings show three types of leadership, namely trustworthy guiding leadership, empowering leadership and autocratic leadership. Our model with three predictors of a spiritual life growing in discernment (spiritual traits, capital and transformation) is partially confirmed, and looks promising for future research. In the discussion, the authors reflect on trustworthy-guiding leadership from the concept of attestation of Paul Ricoeur.