The main purpose of this thesis is to look at how and why some strikes are more successful than others by applying mobilization theory and organizational leaning (OL) theory in the case of the Korean banking sector. It aims to observe the relationship between the effectiveness of mobilization and OL in unions by looking at how learning from previous strikes influenced strategy-making and outcomes of subsequent strikes. By focusing on four strikes in the Korean banking sector, the research explores how OL in unions affects the effectiveness of mobilization. It is thus intended to revisit and contribute to the existing theories of mobilization and OL. The sector has undergone massive restructuring since the national financial crisis, which was part of an Asian foreign currency crisis, in 1997. The Korean Financial Industrial Union (KFIU) organized four strikes between 1998 and 2003 against the restructuring in order to protect employment security. The union failed to gain satisfactory results at the first and third strikes, but were successful at the second and fourth actions. The evidence, based on interviews and primary and secondary documentation, from these four strikes suggests that the more successful results derived from the existence of positive learning (or OL) from previous strikes. In other words, when the union conducted higher-level learning, such as the adjustment of overall norms or rules and the change of organizational structures, it was able to increase strategic capacity. It was able to devise a more effective strategy, thereby more effectively mobilizing resources and opportunities. This, in turn, led to successful outcomes from the following strike. Studying the learning processes in unions reveals the function of dialogical organization in power (or mobilization). Thus, unions are more likely to succeed in mobilization when they conduct meaningful dialogical learning.