This article examines the external and organizational factors behind the coalition dynamics of two labour unions representing a different mix of employment contract types – temporary and permanent – that led the 2007 Irregular Workers Movement in South Korea. Drawing on semi-structured interview, video, newspapers and internal document data, we find that while political opportunities drove the two unions to come together, broad alliances formed around the coalition on the issue of job security of irregular workers marginalized the union with predominantly regular workers. Organizational differences that seemed complementary at first hindered a collective identity from forming and became a source of resentment as strikes continued on. Varying progression of negotiations not only reduced the benefits of claims coordination and collective action but also invoked otherness among them. Lack of trust and recognition did not allow for even a loose cooperative differentiation relation
