With the increasing market share of retailer brands, many authors have paid considerable attention to retailer brands. Before market liberalisation in 1996 in Korea, retailer brand market was led by the supermarket retailing format, although the first retailer brand product was developed by the department store format. In parallel with the entry of foreign multiple retailers, the retailer brand market has experienced rapid growth. Particularly, the expansion of Tesco UK with well-established retailing know-how into Korea has encouraged Tesco Korea to actively get involved in retailer brand program. As a result, Tesco Korea has led retailer brand market in the Korean marketplace. The research starts with the question of why Tesco Korea has achieved such a higher retailer brand share. Accordingly, this study is to explore how Tesco UK has transferred its own retailing knowledge into Tesco Korea, in terms of retailer brand program development. In order to explore why the retailer brand share of Tesco Korea is higher than that of its counterparts, the author adopted in-depth interview with prepared-questions and store observation as a research methodology. To examine working process as well as information flows within Tesco Korea and from UK to Korea, in-depth interview method is one of the most suitable research methodologies, because of the difficulty of quantifying information or data related to work flows. In addition, to increase the validity of information, the researcher had interviews with Tesco Korea supplier and store personnel. Based on these research techniques, this research explored how Tesco UK has influenced or advised Tesco Korea, particularly, from the point of view of knowledge transfer. Since the entry of Tesco UK into Korea as a joint-venture, the retailer brand market share of Tesco Korea has continuously increased. It would be expected that Tesco UK has helped Tesco Korea to settle down in the Korean market. During interviews with Tesco and a Tesco supplier, the researcher found that Tesco Korea has obviously taken an advantage of retailing know-how created by Tesco UK. Furthermore, the retailer brand development and handling process of Tesco Korea has been operated with the help of Tesco UK. This might mean that Tesco UK has directly or indirectly an impact on the improvement of Korean retailer brand development skills. As a mechanism to transfer retailing knowledge developed in the home market into the host market, one of the international retailers, Tesco UK has adopted many different ways such as annual meeting, trading meeting to import or export own retailer brand products, offering of operation manual developed by Tesco UK and buyer cooperation between Tesco UK and Korea, in order to share information. Through these communication techniques, the knowledge of Tesco UK has been transferred to Tesco Korea. This research accordingly suggests that retailer brand market share is apparently related to how sophisticated or advanced the knowledge of the retailer brand development and handling process of retailers are. It is also demonstrated by this research that advanced development and handling skills make a considerable contribution to increasing retailer brand share in markets with a lower share or no presence of retailer brands.