Saint Nektarios' Theological work is deeply rooted in the biblical and patristic tradition. The purpose of his theological writing was two-fold: to fill in the lack of Orthodox Christian theological literature and make it more widely available, and to enlighten and teach all the faithful members of the Orthodox Church. With this in mind, he composed his theological works with a high level of academic rigour, all the while keeping them accessible to a wider readership, true to the saint's pastoral heart. In Part One, we collect two lengthy treatises--the first being about the One, Holy, Catholic, and Apostolic Church, and the second about Holy Tradition--with a shorter treatise about the Church as a supplement to the first. These works will greatly benefit anyone curious about the Orthodox Church, as well as its members who seek to deepen their understanding of the Church and its heritage. In Part Two, we collect an in-depth treatise which explores the sacraments of the Orthodox Church, followed by a shorter treatise which focuses on Orthodox Christian worship. These works will greatly benefit anyone curious about the Orthodox Church, as well as members who seek to broaden their understanding of the holy sacraments, and consequently deepen their experience and participation in them.