The aim of this paper is to discuss Daniel Quinn`s embarkment on a quest for identity in Paul Auster`s City of Glass. Living with the memories of his wife and son who are now dead, the protagonist, Daniel Quinn, loses his identity and cannot decide whether he is real or fictitious. Within this identity crisis he is situated in a conflict between the view of his self and of the social norms. Instead of being integrated into society, he lives in solitude. He confines himself to writing detective stories under the name of William Wilson. Max Work is the “real” detective of the stories. Therefore it can be said that Quinn takes on multiple identities. What make matters worse, the problem of his identity becomes more complex when he takes on the identity of Paul Auster, an assumed detective, and gets involved in the “Stillman case.” The Auster-character tells Quinn that he is writing an essay on the question of the authorship of Don Quixote. At this point, the question of identity that develops in City Of Glass transforms into one of the author`s identity. However, there is no means of answering the question clearly in the post-modern era.