Linking carbon emissions trading systems across countries has become an important tool for global emission reduction. The three high-emission Asian countries, China, Japan, and South Korea (ROK), all have initiated carbon trading and published ambitious Intended Nationally Determined Contribution targets. Since 2016, the three countries have discussed establishing a long-term unified market for carbon emissions trading, and have sought a scheme for such exchange. This study aimed to investigate whether linking the carbon emissions trading systems of these three countries could potentially achieve more ambitious emission reduction targets. A dynamic energy-environmental version of the Global Trade Analysis Project model was used to simulate carbon market linkages across the three countries. The results indicated that a linked China–Japan–ROK carbon market would be highly cost-effective, have positive economic benefits for all three countries, and improve the carbon market’s liquidity and transaction scale. Under a scenario with no carbon market linking, the economic losses in China, Japan, and ROK would be $51.55 billion, $13.55 billion, and $74.19 billion, respectively. Meanwhile, with carbon trading linking, the losses would be reduced to $47.08 billion, $5.37 billion, and $9.10 billion, respectively. Therefore, a joint China–Japan–ROK carbon market could greatly promote the adoption of market-based tools for emission reduction.