This research was conducted to describe the characterization of John Forbes Nash as the main character of the Novel “A Beautiful Mind” by Sylvia Nasar. This research used the descriptive qualitative method. Descriptive qualitative method used the data in the form of words. The technique of collecting data of this research was the documentation method based on the data used of this research consisting of all of the expressions, utterances, or dialogs describing the main character John Forbes Nash. The researcher used theories of Roberts about ways to analyze the characterization of the main character in the novel. The results of this research showed that the researcher found 3 ways of characterization. There are (1) The figure of speech used by the author, (2) The behavior of the characters described, and (3) The conversation between the characters described.