Purpose: The purpose of the study was to examine the motivational factors of propensity to be a mentor by managers in a formal mentoring in organisations. The author addresses the importance of intrinsic and extrinsic motivations and examines their relation to the propensity to mentor. The second objective was to critically analyse whether managers deciding to mentor do so for egoistic or altruistic reasons - for self-benefits or others’ benefits. The third task concentrates on the role of extrinsic motivational factors, especially additional remuneration on the propensity to mentor. Methodology: For this study, the author applied quantitative research among Polish managers working in medium and large size organisations. The author examines the correlation between dependent and independent variables and addresses the impact of control variables as moderators. Findings: First, the results support managers’ high propensity to mentor in a formal mentoring programme. Second, the study finds that intrinsic motivation was the salient factor taken into consideration in the propensity to mentor, whereas extrinsic motivation exerted very little influence. Third, the study confirms a pattern of motivational pluralism based on the fact that both kinds of intrinsic motivators in the propensity to mentor - for the benefit of oneself or others - appear equally significant. Fourth, the research finds that additional remuneration does not motivate managers to mentor. No moderation effects of age, gender, kind of organisation and carrier level on the propensity to mentor were observed. Research implications: The confirmation of Polish managers’ high propensity to mentor contradicts conventional wisdom in some organisations that managers overloaded with work are unwilling to mentor. The finding that managers want to be mentors may encourage organisations to implement mentoring programmes without fear of a shortage of prospective mentors. Based on observed behaviour and the importance of motivational factors, this study delivers valuable guidelines on the recruitment and selection of mentors for HR departments. The results that managers exclusively follow intrinsic motivation in the propensity to mentor should be considered in designing the methodology of mentors’ selection.