The article analyses the influence of Ancient Greek philosophy and mythology, noticeable in the poetry of Sophia de Mello Breyner Andresen. The results of the analysis show that Sophia de Mello’s poetry, seemingly non-philosophic, is based on the ideas close to the theories proposed by ancient philosophers from Pre-Socratics philosophers to Socrates, Plato and Aristotle. The ideas of the unity between the human being and the Universe, as well as Plato’s theory of the Truth, the Good and the Beauty gain the special importance for the Portuguese writer. The ancient myths are reinterpreted by Sophia de Mello. The Ancient Greece is represented as the symbol of harmony between the human being and the Nature.