In order to more fully understand the importance of same‐gender competition in female supervisor–subordinate working relationships, this study examined the effects of supervisor gender on promotion probabilities for Korean female managers with or without managerial qualifications (e.g. mentoring participation and job ranks). Using a balanced panel sample of 568 Korean female managers in each of four waves (in total, 2272 female managers over 7 years), we conducted a multinomial logistic regression analysis to estimate the promotability of female managers. Our findings showed that mentoring participation negatively affects promotion probability for female managers when they have female supervisors (vs male supervisors). Competitive interdependence can be exacerbated between female managers and female supervisors, especially when they are qualified to compete for the same resources and opportunities, which are limited for female managers and supervisors. Key points: Mentoring participation reduced promotion probabilities of female managers with female supervisors compared to male supervisors. Competitive interdependence between female managers and female supervisors is exacerbated especially when managers are qualified to compete for resources and opportunities that are limited for the group of females. Organizations should make efforts to create and sustain environments where their performance evaluations are based on job‐related skills and abilities, and objective achievements, rather than gender‐based perceptions.