This study examined the primary school principals’ perceptions of ‘trust’ in their mentoring experiences at different career phases. Both quantitative and qualitative methods were used in the study. The Primary School Principals’ Mentoring Questionnaire previously developed by the researchers was applied to 1462 primary school principals in Istanbul. As a follow-up study, focus groups were carried out with 50 school administrators at various career phases. Results of the study showed that in different career phases, trust played a crucial role in maintaining the collegiality in the principals’ mentoring experiences.