China’s sudden application to join the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) in September 2021 has broad implications for South Korea’s economic relations with China, Japan, and the United States. In the past, Korea frequently debated but invariably postponed deciding whether to participate in negotiations on the CPTPP, despite the substantial benefits to be gained from doing so. However, China’s application has prompted Korean officials to get off the fence and apply as well. As China moves to deepen its ties to regional partners, Korea needs to follow suit, complementing the ongoing implementation of the Regional Comprehensive Economic Partnership (RCEP) with expedited negotiations to join the CPTPP and participation in the US-led Indo-Pacific Economic Framework for Prosperity (IPEF). Korean participation in the RCEP, CPTPP, and IPEF is desirable and mutually reinforcing and should allow Korea to sustain its strong commercial interests in both the US and Chinese markets.