Public health and global health practitioners need to develop global health diplomacy (GHD) skills to efficiently work within complex global health scenarios, such as the current coronavirus disease (COVID-19) pandemic. Problem-based learning was used as a framework to create a scenario-based activity designed to develop GHD-related skills. The application and effectiveness of this scenario-based activity to develop GHD-related skills were assessed. A mixed-methods approach involving a self-administered survey and one focus group discussion was used. The survey collected baseline participant characteristics as well as understanding and improvements in GHD-related skills using a 5-point Likert scale. The focus group was audio-recorded and thematically analyzed using both inductive and deductive codes. Data integration was achieved by connecting and weaving. Method and investigator triangulation techniques were used. Participants self-reported significantly better postscenario-based activity responses when asked about their understanding of diplomacy, negotiation, communication, and how to address public health emergencies (P < 0.01, Wilcoxon signed rank test). Most participants either agreed or strongly agreed that their GHD-related skills improved with participation in the scenario-based activity (diplomacy = 55.6%; negotiation = 66.5%; communication = 72.2%; addressing public health emergencies = 72.1%). Overall, qualitative data were consistent with results obtained using quantitative methods. The scenario-based activity was effective for improving the self-reported understanding of GHD-related skills. The scenario-based activity was also effective for developing the selected GHD-related skills (as self-reported). This scenario-based activity is likely to reduce cognitive load and avoid participant overload, thereby facilitating learning. Further research is required to elucidate its long-term impact on skills development.