The article analizes the problem loan words in the Portuguese-written works by the Portuguese philologist of 16th century F. de Oliveira. The material of investigation are “Grammatica da lingoagem portuguesa” (“Grammar of Portuguese Language”), “Arte da guerra do mar” (“Treatise of Sea Warfare”), “Viagem do Fernão de Magalhães” (“Voyage of Fernão de Magalhães”), “Liuro da fabrica das naos” (“Book of Shipbuil­ding”). The author of this article studies the F. de Oliveira’s point of view on loan words and compares its with the vocabulary of investigated works. The word groups of diffe­rent etymology are discovered with the method of total selection: aboriginal vocabulary, Graecisms, Latinisms, Germanisms, Arabisms, Gallicisms, Hispanisms, Exotisms, Internationalisms. The vocabulary of all investigated word groups is also analyzed with the method of semantic distribution.