The ancient biographical tradition, mainly represented by writers such as Nepos, Suetonius, Plutarch and the authors of the Historia Augusta, has been the subject of classical studies for a long time. Most investigations have focused on the analysis of what the extant sources have to say on certain prominent historical figures and the socio-political context in which they occur. In addition, philological studies have examined the narrative structures of biographical texts and have viewed them as literary products, not just as purely historical documents. However, what has been neglected thus far is the exploration of the roles of animals in Graeco-Roman biography, although they are more or less omnipresent and fulfil different functions. This article considers the various relationships between humans and animals, as described in Suetonius’ Lives of the Caesars. Special attention is devoted to the ways in which the actions of humans and animals are interwoven in the narrative and what this says about the literary character and intention of the work.