Introduction: Serious Games (SG) are an educational strategy used in the health professions with positive results in teaching diagnosis and facilitating the application of concepts and knowledge transfer. A type of SG is the branching scenario, which has the potential for a linear story or multiple options to achieve learning goals. There must be evidence for this type of SG's instructional design (InD) and usability. Objective: Propose an InD for the branching scenario and rate its usability.Materials and methods: We conducted a two-phase study. In the first phase, we drafted an InD based on the literature review, and then, we applied an expert validation process through a modified Delphi technique. With the consent of InD, we built five branching scenarios. In the second phase, we apply an instrument to measure the SG usability of the branching scenarios in a cross-sectional study with 216 undergraduate medical students.Results: A proposal for an InD for branching scenarios was elaborated. This InD has five dimensions with steps and definitions that help the designer fulfill the requirements for the SG. With the InD, we developed five branching scenarios for undergraduate medical students. Finally, the rates for the usability of the branchings had high scores. The branching SG with multiple options offers different outcomes for the same clinical problem in a single activity.Discussion: The proposal of a specific InD for branching scenarios considered SG theory and was tested, at least in user usability. The steps proposed include the specificity of the requirements of an SG, such as levels, checkpoints, avatars, and gameplay characteristics, among others, in contrast to the other InD that do not explicitly consider them. One of the limitations of this study is that we applied it only using the H5P software to develop branching scenarios with no other evidence of the performance of the InD in different contexts or platforms.Conclusions: We propose using an InD to construct branching scenarios. This kind of SG has specific characteristics for its correct operation. Using structured steps in developing SG improves the probability of developing decision-making skills. Using an instrument to assess the usability of at least one dimension of the SG is also recommended to identify opportunity areas.