Background: International students, especially Chinese-speaking students, who grew up with collectivist values and the linguistic characteristics of the Chinese language - face a higher risk of mental health issues due to the challenges of geogrpahical, linguistic and cultural transitions when studying abroad. While digital technology has shown promise in supporting mental health, few studies have focused on designing tools specifically for Chinese-speaking international students and the challenges they face. Objective: This study aimed to design and develop a self-directed digital mental health support tool that provides culturally safe and appropriate support for international students. Methods: A co-design approach was used across two study phases - Phase I: Interviews and Phase II: Co-design Workshops - to explore the design implications of the digital tool. Inductive thematic analysis was conducted to extract design insights and solutions. Results: Findings revealed that participants faced a wide range of challenges arising from cross-cultural, academic, and daily life demands, which further contributed to a variety of negative emotions. These findings highlight the critical need to improve mental health awareness, literacy, and help-seeking intentions in this vulnerable group. These insights informed the design that emphasized the integration of culturally adapted resources with self-directed learning tools. Conclusions: Based on the findings, a personalized, self-directed and culturally adapted design has been proposed that creates a bridging pathway linking students’ immediate challenges with mental health education and support. This design offers a clear set of implications for enhancing international students’ mental health awareness, literacy, and help-seeking behaviors, thereby providing essential support for this population. Clinical Trial: Not applicable, RCTs approach is not included.