This study investigated the relationship between trait gratitude and mental health among Chinese college students, with a specific focus on the potential mediating mechanisms of the Tangping (lying flat) tendency and positive self-esteem. A cross-sectional survey was administered to 828 undergraduate students in China, utilizing the Gratitude Questionnaire (GQ-6), the Tangping Questionnaire, the Positive Self-Esteem subscale of the Rosenberg Self-Esteem Scale, and the General Health Questionnaire (GHQ-12). Correlation analyses revealed significant associations among trait gratitude, the Tangping tendency, positive self-esteem, and mental health. Path analysis supported a parallel mediation model rather than a sequential one. Specifically, trait gratitude was associated with mental health not only directly, but also through two distinct and independent pathways: one involving lower Tangping tendencies, and another involving higher positive self-esteem. These findings suggest that gratitude is linked to college students’ mental well-being through dual, non-interfering mechanisms, lower passive coping behaviors alongside higher proactive self-evaluations. The results may inform targeted psychological interventions in higher education aimed at supporting resilience within competitive academic environments.