The article collects and analyses philosophical terms formed in Latin by fourth-century rhetorician and philosopher Marius Victorinus (c. 285–360s C.E.) as a result of his translation from Greek sources. The study examines primarily his theological treatises: the Ad Candidum Arianum (De Generatione Divini Verbi) and the Adversus Arium. It undertakes a quantitative and qualitative examination of these terms by studying two linguistic mechanisms which constitute ‘term-formation’ in Latin: lexical innovation and lexical augmentation. Both functioned as important linguistic and conceptual devices in Victorinus’ translations. The article also examines the theological contexts of certain metaphysical terms to understand further their similarities and differences, not only in Victorinus’ translations, but also in earlier uses of central Latin philosophical terms, e.g., essentia and substantia. The article concludes that Victorinus was more didactic than his philosophical predecessors such as M. Tullius Cicero, Seneca the Younger or Apuleius of Madaura, preferring literal translation (particularly morphological calquing) rather than semantic extensions or metaphorical usages (lexical augmentation). By using neologisms formed using derivational word-formation processes and, on rare occasions, loan-words from Greek, Victorinus adopted an approach of adapting Greek terminology with a high degree of precision in Latin, from a range of sources including Christian, Neo-Platonist, and Gnostic authors. He thereby introduced a new Christological vocabulary in the Latin tradition, making him a significant intellectual figure of the fourth and fifth centuries. Although by no means as dominant as others, such as Augustine or Boethius, Victorinus would nonetheless come to exert influence over later Christian philosophers in the Latin West, particularly during the Scholastic period of the Middle Ages.