Framed by institutional theory, this study reassesses the influence of seniority on (HRM) in South Korea today. We analyze first the overall influence of seniority in business, second its significance for career progression (i.e. promotion), and third its relation to individual performance orientation. By conducting in-depth interviews among local and expatriate managers, we find that the role of seniority is still pronounced. Seniority-based promotion remains significant, and individual performance evaluation systems, as are typically found in Western countries, hardly fit the cultural environment and tend to be ineffective. By contributing to the extant theories on institutional dynamics and the convergence–divergence–hybridization debate alike, our results strengthen the culturalist approaches, holding that informal institutions persist and do not disappear quickly. Further, rather than moving towards global convergence, we see the Korean HRM system as being in a state of hybridization caused by coercive isomorphism resulting from experimentation with foreign best-practice systems. As a result, some HRM practices are dysfunctional. We recommend that firms should reinterpret their valuation of individual performance towards team achievements and pay more attention to the optimal team composition.