The current COVID-19situation has forced many tourism businesses to close. Tourism workers have suffered chronic stress, discouragement, despair, and failure to find solutions for their businesses, resulting in deteriorating mental health. A psychological capital intervention (PCI) is therefore deemed necessary as it promotes the mental well-being of tourism workers. This article reports the development of a web-based PCI for the mental well-being of tourism workers and an investigation of its effectiveness using a mixed-methods intervention design. A qualitative approach was used to develop the intervention by conducting in-depth interviews with 20 tourism entrepreneurs. A content analysis was carried out. The intervention was tested through an experimental research design. The sample comprised 600 tourism workers who undertook a web-based PCI. Data on their mental well-being were collected before the intervention and 1 month afterward and analyzed using ANCOVA. The research revealed that 4 themes are needed for the intervention: having a goal, tolerance of difficulties, inspiration from a role model, and the appropriate way of thinking. An effectiveness examination showed that the web-based PCI improves mental well-being. In conclusion, this web-based PCI, which focuses on developing strengths, effectively improves the mental well-being of tourism workers facing difficulties during the COVID-19 pandemic.