Purpose: Drawing on conservation of resource theory, social cognitive theory and person-environment fit theory, this study aims to investigate the impact of servant leadership and self-efficacy on service quality in fitness centers. Patients and Methods: Cross-sectional data came from 771 employees of fitness center. All participants completed the perceived servant leadership scale, self-efficacy scale and service quality scale. The polynomial regression and response surface analysis techniques were used to investigate the mediating influence and boundary conditions of self-efficacy. Results: Self-efficacy acts as a mediator between servant leadership and employee service quality, with servant leadership having a positive, substantial impact on both. Meanwhile, regarding the relationship, the level of service quality is inversely correlated with the degree to which servant leadership and employee self-efficacy are aligned. The smaller the degree of alignment, the lower the level of employee service quality. Conclusion: The findings of this study can help fitness centre practitioners better improve the service quality of employees through service-oriented servant leadership during the COVID-19 pandemic, thereby contributing to the development of the sports and service industries. [ABSTRACT FROM AUTHOR]