The current paper presents lessons learned from a research-to-practice partnership between mentoring program practitioners and researchers that focused on the development and implementation of a cultural humility training for volunteer mentors. Using multiple data sources (e.g., training materials, field notes, mentor surveys), we present a description of the research-to-practice partnership and the Culturally Smart Relationships pilot training content. We generate practice-oriented lessons to inform future cultural humility training work with staff and volunteers in youth programs. Our lessons reflect recommendations that emerged from five project phases: (a) organizational commitment to justice, equity, diversity, inclusion; (b) training curriculum and logistical planning; (c) "To Zoom, or not to Zoom''; (d) facilitation of the training; and (e) post-training and ongoing support. The pilot training content and lessons learned have implications for youth programs by elucidating training as one component of a broader approach for equity in youth developmental program practice.