Isidore of Pelusium (360-449/450?) left behind an extensive yet understudied corpus epistularum of approximately 2012 letters, transmitted initially in the monastic environment in which he was active. The sample gathered for this paper comprises 14 letters addressed to the character “Didymus,” divided as follows (6+1+7): 6 letters addressed to the “priest Didymus” (681, 682, 1249 [v. 28], 1448 [v. 167], 1515 [iv. 20], 1949 [v. 534]), 1 letter addressed to both “Didymus and Heron” (1818 [v. 433]), and 7 more to “Didymus” without any title attached (199, 201, 204, 205, 281, 330, 331). This selection is important because those letters for which the identification of the addressee as Didymus the Blind can be proven are among the oldest of the whole Isidorian corpus (shortly before 380). Yet the matter is not clear since, for instance, in letter 1448 Isidore addresses Didymus as σοφώτατε (also letter 331 seems to testify to Isidore’s personal acquaintance with Didymus the Blind), while in letter 1249 (and also in 681, 682) the priest Didymus seems rather a disciple of Isidore, and thus, the addressee is less likely to be identified with Didymus the Blind. Thus this paper will tackle (a) historical (addressee, date and place of composition), (b) literary (content, intent), and (c) exegetical issues in order to establish to what extent we can attribute any of these pieces as addressed to Didymus the Blind, and, if at all possible, to grasp some aspects of their relationship.