Under the context of neoliberal globalization, governments have pursued marketdriven economic reform policies and large firms have adopted the business model of shortterm profit maximization. In this context, intensification of labor polarization has produced growing concerns over the solidarity crisis faced by the labor movement in Korea, which reveals serious weaknesses in internal and external solidarity requiring rectification in order to overcome labor polarization. Internal solidarity of the labor movement in Korea has been weakened by union members’ attitude of self-interest toward job security and economic gain, by fragmented co-worker relations, and by intensified competition among activist factions for political power within unions. The most crucial factor constraining external solidarity of the Korean labor movement is the legacy of enterprise unionism, which has produced differentiated interest structures between organized and unorganized workers, while hindering the two worker groups from fostering a common ground of union activities and political vision. Reflexive leadership of labor movement, substantiation of industrial unionism, and fostering of communitarian activism are recommended for revitalizing labor solidarity.