This study explores the commonality and variation of non-regular workers’ struggles in Korea by drawing upon 30 major dispute cases which have taken place since 2000. The common features of those struggles are characterized as defensive claim-making, employer’s determined union-busting, protracted struggle outside workplace, transgressive protest repertoire, reliance on external solidarity, third actors’ mediation, dispute recurrence and union’s organizational instability, and protest against large firms. At the same time, the non-regular workers’ struggle shows a great deal of variation in outcomes (i.e. bargaining gains and union membership) and key attributes (i.e. repertoire, duration, timing) of those struggles. The different outcomes of the struggles are closely correlated with the attitude of regular workers unions as well as the extent of external solidarity toward non-regular workers’ struggles, with some contingencies (i.e. public meaning of the struggle, the content and timing of related legal decision by the government or the court, the industry union’s involvement, and claimants’ self-sacrificing protest) creating outliers from this patterned relationship. The outcome of non-regular workers’ struggles is also correlated with their repertoire and duration in a polarizing form like the spirals of moderatization (better outcome – low-risk repertoire – shorter duration) and extremization (worse outcome – high-risk repertoire – longer duration).