This research aimed to study and establish the mental preparedness model of Thai athletes during the COVID-19 pandemic in preparation for the 19th Asian Games. This study employed a mixed methods approach, involving 409 participants (217 males and 192 females) selected through a lottery system, ensuring equitable representation across the 19 types of sports. Additionally, six participants were included for qualitative data gathering. The research designed a comprehensive questionnaire to collect data, which included the Sports Stress Management Skills in Thai Questionnaire, Questionnaire on Mental Readiness for Competition, 'Motivation to Participate in Sports Activities in Thai' Questionnaire, Self-Confidence Questionnaire, Mental Toughness Questionnaire in Thai, and the Mindfulness in Sports Questionnaire in Thai Version. Data was collected using a traditional questionnaire and an online questionnaire accessed via QR codes. Structural Equation Modeling was employed for data analysis. Qualitative data were gathered through interviews. The study's results revealed the development of a mental preparation model for Thai national team athletes during the COVID-19 outbreak. This model emphasizes the significance of mindfulness as a crucial factor directly influencing psychological readiness. Furthermore, mindfulness exerts an indirect influence through four intermediary variables: motivation, stress management skills, confidence, and mental toughness. Significantly, qualitative data highlighted adaptive mental resilience and mindfulness as key factors in fostering mental readiness among athletes, especially during challenging periods like the COVID-19 outbreak. These factors encompass effective stress management, balanced motivation, self-confidence, professional guidance, adaptive mindset, support systems, and long-term planning. This model integrates various elements of mental preparation, with mindfulness positioned as the central pillar.