The manifestations of real-life often appear in the novel. Suicide is one of the real-life phenomena adopted in novels whichis often caused by anxious feelings. Anxiety is a term for nervousness, fear, and worry disorder. This research intended to find the symptoms of anxiety through the characterization of Hannah Baker. The researcher also analyzed the defense mechanisms used by Hannah Baker to cope with her anxieties in the novel. This research uses a qualitative method with a psychoanalytic criticism approach. The primary data source of this research is Jay Asher’sThirteen Reasons Whynovel. Personality theory by Calvin S. Hall was used to analyze this research as well the articles from other writers and the internet. Based on characterization theory, it was found that Hannah Baker has anxiety with her friends through showing. All the anxieties are categorized as realistic anxiety, neurotic anxiety, and moral anxiety. Then, there are defense mechanisms used by Hannah Baker to overcome her anxiety such as sublimation, displacement, and denial through showing. It can be concluded that in the novel, the defense mechanisms do help Hannah Baker reduce her anxiety for a while, but it is not enough and she still chooses to end her life.