The world's aging fleet of nuclear power reactors faces decommissioning. Because decommissioning is implemented through a series of procedures, and this process changes the links between some industries, its economic impact needs to be investigated. This study compared the economic impacts of three nuclear industry sectors nuclear generation, nuclear power construction, and nuclear decommissioning using input-output analysis in South Korea, the first Asian country that has declared a nuclear phaseout. The study also traced changes in the structure of the nuclear industry during the Korean nuclear phaseout and the consequent economic impacts. The study found that the implementation of the nuclear phaseout will lead to a decrease in the induced outputs and the value added of nuclear industries in South Korea; however, this would be offset by deploying more renewable energy. In addition, the temporal impacts on individual sectors vary depending on changes in the number of reactors being decommissioned and the expenditure profile of the nuclear decommissioning sector. The findings call for policy measures that support a soft landing for nuclear industry sectors and related stakeholders, timely development of necessary technologies, and transparency in public communication. This study provides a methodological approach and input structure that can be used for studies in other countries.