A particular element of computer games which significantly affects the gaming experience is avatars, i.e., representations of virtual players. In particular player-avatar similarity is related to the game experience, however, the results of previous studies are not conclusive. There is also a lack of research in which participants actually create their own avatars. The first aim of this study is to check whether there is a relationship between the player-avatar similarity and the game experience: game efficacy, game enjoyment and immersion. As a second goal the study examines gender as the mechanism responsible for the relationship between avatar player-similarity and game experience: game enjoyment, game efficacy and immersion. In the study (N = 130) participants created their avatars, played designed computer game Characterium and assessed their experience. The results demonstrate that player-avatar similarity was positively related to immersion level (but not to game efficacy and game enjoyment). Gender was not a significant moderator of the relationships between avatar similarity and game efficacy, game enjoyment and immersion. We consider this study to be a step forward in better understanding the mechanisms underlying the relationship between player-avatar similarity and game experience. For the first time, the relationship between player-avatar similarity and immersion was demonstrated in the condition of creating an avatar by the subjects and controlling it in the game. We also identify potential reasons why our hypotheses have not been confirmed.