This chapter delineates the foundational characteristics of the Korea Fair Trade Commission’s merger enforcement approach. It proceeds to systematically examine the conceptual foundations and analytical methodologies employed in evaluating the competitive effects of mergers. Traditional tools such as market share analysis and concentration indices are discussed alongside modern empirical techniques, including natural experiments, merger simulations, and Upward Pricing Pressure (UPP) metrics, particularly in the context of horizontal mergers. For non-horizontal mergers, the chapter explores advanced methodologies such as vertical arithmetic, bargaining models, the vertical Gross Upward Pricing Pressure Index (vGUPPI), Cournot competition effects, and the implications of eliminating double marginalization. These diverse analytical instruments provide a robust foundation for assessing the nuanced competitive dynamics across merger types, thereby supporting a rigorous and sophisticated regulatory review process. The chapter concludes with introducing significant merger regulation cases in Korea, including Hyundai Motor—Kia Car in 1999, Moohak Soju—Daesun Soju in 2003, Hite Beer—Jinro Soju in 2006, Eland Outlets—Carrefour in 2006, eBay—G Market in 2009, Microsoft—Nokia in 2015, SK Telecomm—CJ HelloVision in 2016, Delivery Hero—Woowa Brothers in 2021, and Korean Air—Asiana Airlines in 2022.