This article attempts to make known the Epistolary, up to now inedited, of Sister Josefa de los Dolores Peña y Lillo, chilean dominican nun from the XVIIIth century. Her text constituted by sixty five letters, addressed to her father confessor, the jesuit Manuel Alvarez. These letters are kept in the Archive of the Dominican Monastery of Santa Rosa de Lima in Santiago, Chile. The letters seem a manifestation of confessional discourse which the nuns had to write by order of their father confessors or ecclesiastical autorities. However, the Epistolary analysis reveals the transformations of that discoursive pattern, which Sor Josefa’s writing constitutes itself in the support of a selfknowing process and in a construction of woman identity, which is not recognized only in her religious vocation and virtues, but also in her knowing capacity, wisdom and words management.