Division among Christians within the Church has often been a problem. From the beginning of Christianity, we find these indications of divisions within this one and only Church of Christ (Cf. 1Cor 1:10-16; UR 3). However, even if the history of the Church shows a long experience of divisions, it has never lacked strong and devoted Christians who have worked for the good of Church unity asserting the credibility of the Gospel. In that regard, Saint Augustine of Hippo stands as one of the most prominent figures. His struggle to restore Christian unity damaged by the Donatist schism in the north of Africa is beyond compare. It is in his involvement with the Donatist controversy that Augustine appears explicitly to be a devoted Apostle and pioneer of Christian unity. Augustine as a Catholic bishop and defender of Christian unity put himself in the service of reconciliation, employing all the means of his genius and the ardor of his heart. Therefore, his doctrine on the Church and Sacraments, the methods he employed, and all the effort he exerted to restore unity in the Church of Africa is still a source of inspiration for modern ecumenism. This work states the conviction that in matters of Christian unity, Saint Augustine remains an undisputed authority and a key reference for pastoral and academic endeavors.