In recent years, there has been a significant increase in teacher turnover, which poses a notable challenge to improving the quality of education. Individual characteristics such as teacher motivation, self-efficacy, and job satisfaction have been linked to the tendency for turnover. However, the exact connections between these attributes remain somewhat unclear. To address this issue, this study applied the Social Cognitive Career Theory to explore the relationships among teacher motivation, self-efficacy, and job satisfaction in middle school settings. Using data from the 2018 Teaching and Learning International Survey, this study conducted a mediation analysis through structural equation modelling to explore how teacher motivation and self-efficacy impact the job satisfaction of 3,835 middle school teachers in Taiwan. The findings reveal that social utility motivation has a direct, positive influence on two aspects of teacher job satisfaction--the work environment and professional satisfaction--and this influence occurs indirectly through teacher self-efficacy. Conversely, personal utility motivation directly predicts teachers' job satisfaction within their profession. By considering teacher self-efficacy as a mediating factor, this study offers new insights into the intricate relationships between teacher motivation, self-efficacy, and job satisfaction.