In this study, we analyze the development of key professional skills for sustainability (KPSS) in university students using serious games (SG) from a sustainability perspective. Sustainable Development Goals (SDGs) were set by the United Nations’ 2030 Agenda for Sustainable Development. Universities are strategic agents in the transformation process towards sustainability. Thus, universities should be committed to promoting such skills in their students through sustainable curricula by implementing active methodologies and using SG for that purpose. KPSS are essential for the development of future graduates. The aim of this study is to determine what KPSS have to be developed through the SG “The Island”, in order to improve the degree of satisfaction towards the incorporation of a sustainable curriculum among the students. The data were obtained using a questionnaire and then analyzed using linear regression models, with their inferences estimated through a goodness of fit test and ANOVA. The first results indicated that implementation of the SG promoted a strengthening of the students' sustainable curriculum through the development of related skills. It was concluded that the key to success in education for sustainable development is to improve the development of strategic thinking, collaborative thinking, and self-awareness, in addition to encouraging systemic, critical, and problem-solving thinking.