This study aimed to investigate the mediating effect of burnout on the relationship between grit and turnover intention of private tertiary school teachers in Region XI. A convergent mixed-methods design was utilized. A total of 303 private tertiary school teachers who were at least three years already in the service in Region XI were selected using purposive sampling technique. Adapted survey tools and interview guide questions were used to gather the essential data. The statistical tools used were mean, standard deviation, Pearson Product Moment of Correlation, and the Sobel z-test. The Colaizzi’s method was utilized to elucidate the qualitative data. The findings revealed that private tertiary school teachers’ level of burnout and turnover intention were low, and their level of grit was high. Moreover, the relationship among these variables was significant. Also, the mediating effect of burnout on the relationship between grit and turnover intention was significant, although it was just partial. The lived experiences of teachers were explained further by the themes revealing personal, work, and client-related burnout; positive dispositions on the teaching profession; underlying reasons for low level of attrition; and invigorating grit and strength as reasons to stay. Furthermore, the impact of these experiences on their beliefs and attitudes included: staying is beneficial, adhering commitment to excellence, and demonstrating positivity in all circumstances. Finally, the quantitative findings corroborate with the qualitative findings.