Critiques of the failing efforts of transitional justice processes in Mexico have dominated the academic literature on the matter. I argue that a primordial focus on the systematic and culture of impunity in Mexican institutions has greatly concealed efforts on the institutionalization of the right to truth. Using a process-tracing methodology based on interviews and documental analysis, I study three specific mechanisms that have been implemented to satisfy the right to truth: a truth commission in Guerrero, a mechanism formed by interdisciplinary experts concerning the disappearance of 43 students in Ayotzinapa, and the truth commission recently created by presidential decree. I propose a causal mechanism that poses the Inter-American Human Rights System as a leverage mechanism in the implementation of the truth pillar in Mexico. Results demonstrate that a causal process exists between the identification of international norms, by norm entrepreneurs; their participation at the Inter-American Human Rights System; the localization of these norms by civil society organizations in their own communities and the impulse of societal pressure in the institutionalization of the right to truth, in Mexico.