This thesis analyses the terms in which collective identity and regional institutions can explain state action towards the unfolding of regionalism in the Andean Community (AC). This analysis develops a constructivist approach that assesses constitutive and casual effects of ideas in order to provide explanations. For the assessment and distinction of these effects, the thesis proposes an interpretive method that consists of focusing on transitive verbs and metaphors denoting causation that state officials and regional bureaucrats use to refer to the role of ideas in orienting state action. The analysis of the explanatory role of collective identity and regional institutions is carried out in three case studies of the AC, namely, Peru remaining an AC member while being reluctant to adopt the Andean Free Trade Zone (FTZ) and the Common External Tariff (CET); collective negotiations of a free trade agreement between the AC and the European Union; and the adoption of the Integrated Plan for Social Development (PIDS). The thesis shows that constitutive and causal effects of ideas are possible to observe in the three case studies of the AC. By observing these effects, the thesis provides a better understanding of a relationship of mutual constitution and causation between collective identity and regional institutions in the AC, and suggests a number of issues that may explain the AC's maintenance despite its little achievements and low material benefits it provides to member states. The thesis also makes a significant contribution to constructivist theorising inasmuch as it provides a method to operationalise constructivism's aim of providing explanations based on the role of ideas. To the study of the AC, this thesis represents a major contribution inasmuch as it is the first work that analyses the views of some of the main performers of state action and of the AC as a regional organisation, which accounts for the closest approach to how member states act in the AC.