Jim Dixon has been a junior lecturer in the history department of a provincial college in England after World War II for eight months when Lucky Jim begins. Dixon is unremarkable in every way except for his sardonic mental commentaries on those around him, which focus on the nuances of other people's voices, appearance, or language. Dixon also vents his frustration with others through faces he makes to himself in private, some of which have actual titles.

At the beginning of the novel, Dixon is a meek man, although his thoughts are not. His indecisive actions and quite demeanor reflect his fear of being fired from his post at the end of the term next month. Dixon's meekness also reflects his fear of hurting Margaret, who he is not attracted to, but to whom he is attached by virtue of their friendship and his concern for her. Dixon's character becomes filled out as he defines himself by what he doesn't like. Dixon despises unnecessary complexity, pomposity, hypocrisy, and those who feel that some people—artists, higher classes, for example—have special needs that ordinary people don't have. From this last conviction arises Dixon's socialism, which fits in with the Labour government atmosphere after World War II in Britain. However, Dixon's feeling that no one has special needs also seems to extend to the unfortunate as well as the fortunate. The knowledge that Margaret wasn't born particularly attractive, for example, does not endear her any further to Dixon. Dixon feels that he has been unlucky as well, but his luck changes over the course of the novel, as he makes the conscious decision to "bet on his luck" for the first time in his life.