Abstract: Socializing is an important part of why people choose to play games and is at the core of many game mechanics. Anxiety and fear about social interactions can lead to withdrawal from socializing in the physical world, yet players with social anxiety preferentially choose MMORPGs — a highly social genre — raising questions of whether social anxiety expresses differently during in-game interactions. In the present study (N=181), we explore whether and how social anxiety translates into MMORPGs. By developing a measure of in-game social anxiety, we find that although fear and apprehension of socializing in the physical and game worlds are related, they differently affect preferences, behaviours, and experiences. Social anxiety in the physical world drives reasons for playing, whereas in-game anxiety affects behaviours, reducing participation in activities related to socializing and difficult in-game challenges. Our findings can inform the design of social games and the links between social anxiety and social gaming.