This study applied multilevel modeling to examine how individual characteristics, such as gender and teaching experience, and contextual characteristics, such as principal leadership and perceived colleague support, influenced Korean secondary school teachers' sense of job satisfaction. Previous research identified teachers with high job satisfaction to have positive influences on their students, making it important to understand teacher job satisfaction not only for teachers but also for students. Using data from a nationally representative sample of 2908 teachers from 150 middle schools, the results indicated that (1) among teachers' individual characteristics, teacher efficacy had significant effects on teacher job satisfaction, and (2) among institutional, school-level characteristics, perceptions of academic climate, support from colleagues, and supportive principal leadership had significant impacts on teacher job satisfaction. The findings of this study provide reason for individual teachers to reflect on their sense of efficacy and the influence it can have on their professional practice. The study also suggests ways to create better education policies on the basis of its empirical data.