The concept of 21st-century skills refers to the knowledge, skills, and emotions that are critical to successfully navigating today’s world. Game jams can act as spaces to develop these skills and thus boost cooperative learning, problem-based learning, or co-creation. Additionally, game jams offer opportunities to improve collaboration and creativity skills, among others. This paper summarizes three years of activities designing and studying game jams to develop 21st-century skills, focused on Mexican students aged 12–16 years old. Data were compiled through direct observation, open-ended questionnaires, and interviews and were subject to thematic analysis in order to construct new knowledge on a previously underexplored topic. The results suggest that game jams are valuable tools to develop 21st-century skills, and, although the outcomes of skill evaluation may vary and may be difficult to verify, the participants reported increased skills, such as creativity or collaboration. Finally, this paper provides recommendations based on the research and practice conducted by the authors on how to use game jams to develop 21st-century skills and different ways to organize game jams, along with the resources needed.