This quasi-experimental study investigated how effective a spiritually integrated, partner-interactive positive psychology intervention (PPI) was in promoting religious leaders’ humility and life satisfaction. Seventy-one Christian pastors and lay leaders self-selected to the waitlist-control (n = 30) or humility-PPI condition (n = 41). Humility-PPI participants completed a 16-exercise workbook with a partner. Intervention effectiveness was assessed using self- and other-report measures. Hypotheses were not supported, in that there was no evidence that intervention participants exhibited greater gains in life satisfaction or in trait, relational, spiritual, or intellectual humility, compared with control participants. Postintervention feedback suggested participants varied in their preferences for specific types of exercises (e.g., insight-oriented, reflective exercises vs. action-oriented, interactive exercises). Self- and other-report ratings showed increased correlation between self- and other-report measures at Time 2 on relational humility measures, thereby giving evidence that the intervention may have been effective in helping participants become more “accurate” in their perceptions of their own relational humility. There is a need for more research on humility PPIs, and the present study indicated primarily null results. More broadly, there is a need for research evaluating PPIs that (a) are tailored to participants’ characteristics or preferences, (b) use a partner-interactive format and a self- and other-report measurement approach, (c) are developed in collaboration with pastors and scientists, (d) are spiritually integrated, (e) are developed for use in faith communities, and (f) focus on leadership development. (PsycINFO Database Record (c) 2018 APA, all rights reserved)