To improve requirement specification skills, it is vital to detect ambiguous requirements in order to correct them later. Thus, to help software engineering students improve their capacity to identify ambiguous user requirements (requirements that do not use technical words) while providing them with a valuable and engaging educational experience, the current study proposes a serious game called DEAR. It consists of a didactic exercise in which participants must move different requirements left or right to indicate whether they are ambiguous or unambiguous. To assess the improvement in students’ abilities in requirement specification and perceptions about the training class when using the DEAR game, we conducted an experiment with 62 participants, splitting them into two groups: one that used the DEAR game and the other that underwent a conventional training session. It was found that, during the training sessions, both groups became more adept at identifying unambiguous user requirements, but there was no discernible difference in performance between them. However, the game group expressed a stronger preference for the training session’s engagement and quality, as well as a stronger sense of having learned how to clearly define user requirements. Overall, the experiment shows that the suggested serious game DEAR may be a helpful teaching tool that yields learning outcomes comparable to those of a chalkboard class while encouraging students to identify unambiguous user requirements in an interactive manner.