In the last years, there has been an increasing interest in the design of video games as a tool for education, training, health promotion, socialization, etc. Usability, which is a key factor in any video game, becomes even more important in these so-called “serious games”, where the users’ special characteristics should be considered, and the game efficacy depends on the users’ adherence and engagement. However, evaluation of the usability of this kind of games requires a redefinition of techniques, methods and even terminology. In this paper, we elicit six research questions and conduct a systematic review of the scientific literature, which resulted in the selection of 187 papers that contained the most relevant responses. The conclusions of this systematic review illustrate the general status of current academic usability evaluations of these games and the main trends in the selection of methodologies and how are they applied. This view may be a very valuable foundation for future research.