After graduating Suzuka Circuit Racing School Formula (SRS-F) at the top of his class in 2004, Koudai Tsukakoshi won every round of the 2005 Formula Dream series to take the championship.
In 2006 Tsukakoshi moved up to the Japanese Formula 3 Championship, competing his debut season fifth. In 2007, he was second in Macao. In 2008, he challenged the Euro Formula 3 series, where he was on the podium four times. In 2009, he debuted in SUPER GT, finishing on the podium twice. In Formula NIPPON, he was the Rookie of the Year.
2010 saw Tsukakoshi win his first SUPER GT race. In 2011, he was fourth overall, with pole position at Round 2 in Okayama and three podiums.
In his fourth year partnering with Toshihiro Kaneishi, Tsukakoshi raced to his season-best third place in the opening round of 2012. In Formula NIPPON, he also won his first race, and was ranked second. After moving to the GT500 class and Keihin Real Racing in 2013, Tsukakoshi was the highest-ranked HSV-010 GT driver, completing the season second.
In Tsukakoshi’s sixth season with Kaneishi, they finished the 2014 season in 12th place. In 2015, Tsukakoshi partnered with Eiki Mutoh. In 2017, he and new partner Takashi Kogure were second place in two rounds. In the following year, they had a second and a third place finish.
Tsukakoshi was sixth with new teammate Bertrand Baguette in 2019, and third the following season.
In 2021, Tsukakoshi aims to win the championship, and finished 6th.
In 2022, he and Nobuharu Matsushita competed for the title until the final round, finished 4th overall.