The aim of this short paper is to highlight nature’s central role in the constitution and progress of human morality, by analysing nature’s multiple characters as displayed in various sections of Seneca’s work. First, the focus will extend to man’s fundamental propensity to good, which belongs to him by nature. Secondly, a virtuous and happy life will be presented as the life led according to nature. In conclusion, research on natural phenomena will be accounted for, as a building block towards moral perfection. The relationship between all the previous traits, mentioned in the cited passages, constitutes the heart of Seneca’s ethical naturalism.