This paper aims to sketch as accurately as possible the moral portrait of one of the recipients of Saint Isidore’s epistles. In addition to the 15 letters addressed directly to Bishop Eusebius of Pelusium, we also find explicit references to him in another 54 letters, but also implicit references in several others. Starting from the observations of Pierre Évieux and Constantine Fouskas, this paper goes a little further in the analysis of the letters, systematizing the reproaches made by Saint Isidore in order to recover a series of details regarding the historical context in which he carried out his activity.