The KT Wiz became the 10th member of the Korea Baseball Organization in 2015. The team is owned by the Kt Corporation. Andy Marte hit .348 with 20 homers and 89 RBIs for the team in its inaugural season, then had another 20-homer season for them in 2016. Han-joon Yoo was named one of the KBO's top three outfielders in the team's debut year, while Ryan Feierabend led the league in ERA (3.04) in 2017 as the team again finished last. They escaped the cellar in 2018 by a slim margin over the NC Dinos; interestingly, both teams would win the Korean Series within three years.
In 2019, the team made huge gains, going to .500 (71-71-2) while Mel Rojas Jr. was named one of the league's top three outfielders. The next year, the team made the playoffs for the first time, finishing second in the league. Rojas won the KBO MVP after nearly winning a Triple Crown (.349, 47 HR, 135 RBI) while Woo-jun Shim led in steals (35). 1B Baek-ho Kang and 3B Jae-gyun Hwang each won a KBO Gold Glove as the best overall player at their position, while Rojas repeated in the outfield; that was quite a jump after the team had two Gold Glove winners (Yoo in 2015, Rojas in 2019) in their first five seasons.
The Wiz then won the 2021 Korean Series for their first title. Key players included Young-pyo Ko (11-6, 2.92), Odrisamer Despaigne (13-10, 3.39, 165 K), Jae-yoon Kim (4-3, 32 Sv, 2.42), Kang (.347/.450/.451, 40 2B< 102 RBI) and Yoo (.309/.409/.418) while 2B Kyung-su Park won the Korean Series MVP.