PurposeThe present study seeks to trace the unionization process of a global top 10 video game company (Company N) in which workers formed the first enterprise union in South Korea's game sector. Drawing upon the analytical framework of Kelly's (1998) mobilization theory, the authors investigated what motivated workers to form a union and what factors facilitated unionization.Design/methodology/approachThis study used a qualitative research method on a single case study basis. The authors collected 41 in-depth interviews with game developers, full-time union staff from the case company and union leaders in their affiliated union, as well as game journalists, labour attorneys, and human resource professionals in the video game industry. The authors had their original data supplemented and triangulated by archival data including union letters and other documents and media reports. They analysed the data using computer-assisted qualitative data analysis software (CAQDAS).FindingsThere are three key findings. First, in the game sector, a high barrier against unionization exists, arising from industry characteristics such as a project-based work system, high mobility, reputation-based hiring, meritocracy, and a continuous influx of game-loving young developers. Hence, although the time was ripe for worker activism, latent grievances failed to be converted into real collective mobilization, resulting in non-organized workplaces for the past decades. Second, the mandatory labour-management negotiations arising from a legal change acted as a key catalyst for unionization at Company N. The newly elected three employee representatives came to identify and develop their own collective interests through the direct experience of negotiations, which greatly augmented their negative emotions and improved their legal consciousness. These three representatives could identify numerous deep-rooted problems, attribute these problems to their employer, and realize that they are ordinary salaried workers different from their employer. Going through the three-month negotiation and post-negotiation period, a set of ordinary game developers transformed themselves into natural union leaders who started a union in the game industry, which was traditionally non-organized. Third, various layers of external factors, such as a sister union, the upper umbrella union, the changed socio-political atmosphere following the candlelight protests for presidential impeachment, and the improved union image facilitated the unionization at Company N.Practical implicationsThis study offers practical implications to governments, union activists, and employers in the game sector and more broadly in the tech industry, where labour-management conflicts are escalating across the globe.Originality/valueOur study of a rare unionization event in the difficult game sector offers a nuanced understanding of mobilization and its process. Theoretically, by introducing the dynamic process of natural leader emergence and spontaneous union formation in a young industry where neither pre-existing leadership nor extant union influence exists, this study suggests that the mobilization process is more complex and variegated than suggested by Kelly's study and subsequent studies. Therefore, this study can advance the current discussion of mobilization mechanisms in the field of industrial relations. Our study also contributes to current research by introducing collective mobilization in a new context, i.e. the young, dynamic game industry in a non-Western country, which is a context that has been under-studied thus far.