It is studied the animal’s legal status in the Corpus Iuris Ciulis Institutiones. Therefore, it is questioned the traditional and reductionist way of thinking that identifies those being simply as things, evidencing clues to sui generis character, through a rereading of the Institutes. To such end, the required Roman Law's history to understand Justinian's work is retrieved. Then, a translation proposition for Institutes' parts which have any animal reference is presented, at which point are shown plentiful of signs that point to a singular law condition. It is realized, upon that, a difference in treatment based on animals' own animality and will, distinguished and classified according to different standards, such as nature and habits, like the categories of domestic, wild, domesticated, and non-domesticated animals. Therefore, clues that disclose acknowledgment of animals' sentience and that these beings truly had right derived from ius naturale are revealed.