This paper deals with the subject of the imperial court according to Ammianus Marcellinus. Using the historical source of Res Gestae, together with modern historian literature, the paper analyzes what and how Ammianus described the imperial court in the period from 353 to 378. AD. The purpose of this work is to research and investigate whether or not there was a bias in his writing, what was Ammianus intentionally emphasizing, and what he might have wanted to hide. In order to see how and to what extent Ammianus described the court and what kind of influence it had on the society, the work is divided into seven tematic chapters. After the introduction, the first chapter deals with Ammianus 's life, along with the history of his work and the attitudes of today's historians about him as a credible author. The paper also elaborates on the court administration, in which the court's terminology, court mobility and the role of the colour purple is defined and explained. The Ammianus account of imperial power is elaborated on the example of Empress Euzebia and Emperors Julianus and Constantius II. The role of agentes in rebus, court conspiracies and secret missions in general are explored as well. The subject of the usurpers Silvanus and Procopius and the role of the court in dealing with them is also presented and explored, specifically emphasizing on Ammianus's role in those situations. The topic of court eunuchs is also discussed, with the emphasis on Eusebius and Euterius, while the last chapter deals with the role of religion in the imperial court, as well as with Ammianus's attitude towards religious issues. These subjects are explored in order to conclude how valid Ammianus's description of the imperial court was and also the extent and the credibility of his work.