This paper argues that, by applying the doctrine of oikeiosis, it is possible to consider a theory of animal action in the Stoic thought. The text asserts that, even when the Stoics accepted the existence of impressions, impulses and assents in humans as well as in animals, the content of these concepts are, in each case, different. In that sense, this paper permits to identify more precisely what is distinctive of animals, and shows how the comparison between human beings and animals states a consistency in the doctrine according to which animals behave according to its nature.