Using longitudinal data on 1,711 female managers in South Korean firms, this study examines how time, culture, and workplace structure affect women’s mentoring networks. Our analyses demonstrate that women with fewer time constraints and who work longer hours are more likely to have a male mentor. However, when motherhood status is considered, work hours and time constraints are not significant predictors of having a mentor for mothers. Rather, organizational flexibility and work-life policies influence whether mothers have mentors, but those mothers who work long hours and display minimal domestic commitments benefit the most from the availability of flexibility. Findings suggest that long work hours and time constraints affect women’s marginalization in workplace relationships, and corporate practices mitigating work hour expectations can alleviate this impact for women with children.