The collective dominance doctrine is considered a useful competition law measure for oligopolists` interdependent coordinations (so-called tacit collusion) which many competition law regimes are ill-equipped to deal with. It can be specifically effective in dealing with long-lasting oligopolies in major Korean industries. However, it has been known as one of the most controversial issues in the contemporary competition law and policy discussions. In particular, the European Commission and the European Courts have long discussed over the doctrine and finally come up with relatively settled law recently. One the other hand, the shared monopoly doctrine, the American counterpart to the collective dominance doctrine has largely been rejected by majority of American courts. It has been debated whether the collective doctrine was recognized also under the Korea Monopoly Regulation Act and there has been some related interpretative unclearness with regard to the presumption of market-dominating undertakings under Section 4 of the Act and provisions of the Merger Assessment Guidelines. In light of the relevant legislative history, legislative texts and competition policies, this article argues that the doctrine is recognized under the Korea Monopoly Regulation Act as well and supports interpretations based upon the doctrine. Further, it also suggests legislative amendments to clarifying the related issues.