This thesis explores the ways in which Suetonius’ De vita Caesarum represents complex characters beyond simple ciphers of virtue and vice. The first chapter maps out three dimensions of characterization demonstrated in ancient writing (baseline, dissonant, and realistic). The second chapter applies this tripartite perspective to the emperor Claudius, in an isolated case study, as a means of reading his complex character construction. The nature of biography only achieves a complete portrait of a person through selective topics and as such the third chapter examines how external descriptions (i.e. physical appearance, dress, and names) create complex characterization. Speech is often the mirror of a man and the fourth chapter observes the ways in which Suetonius makes use of oratory, epigrams, and humour. The fifth chapter looks at how the sexual episodes and escapades of the Caesars provide intimate insights into their personalities beyond being emblems of virtue and vice. All three of these chapters reveal how characters are reinforced, subverted, or imbued with realism in line with the three dimensions initially outlined. Finally, this thesis shows how the very structure of Suetonius’ collection aids his characterizations. The sixth chapter shows how two stock elements of biographical writing, ancestry and death, act to confirm, develop, or complicate the personalities of his Caesars. The seventh chapter treats the collection as a macro-text to show how characterization is informed by appearances across the Lives and how Suetonius creates characters, such as Germanicus and Livia, through extended cameos.