© Universidad Autonoma del Estado de Mexico. All rights reserved. This article analyzes the process of socialization and political radicalization in militants of the Communist Party of Peru-Sendero Luminoso, who participated in the internal armed conflict in Peru between 1980 and 2000. Thus, through a phenomenological design, 16 in-depth interviews are performed, whose content analysis is carried out with support from the specialized software Atlas.ti 7.5. The results allow the identification of macro, meso and individual levels of socialization. Likewise, causal factors and catalyzing circumstances that influence and trigger radicalization are identified. It is concluded that there are not direct causes, but rather a progressive extremist escalation that crosses different levels of socialization, with emphasis on the meso and individual levels, and that exposed to catalyzing circumstances, either by rational or emotional way, leads to political radicalization.