Recent studies show that teacher job satisfaction has declined in Spain over the last decade. Additionally, teacher job satisfaction is significantly lower in secondary education than in lower educational levels. In this paper, we identify variables that contribute to the prediction of teacher job satisfaction in secondary education. We use the Spanish sample (192 schools and 3,339 teachers) participating in the 2013 edition of the Teaching and Learning International Study (TALIS), sponsored by the Organisation for Economic Co-operation and Development (OECD). Employing hierarchical linear models, we assess the importance of teacher variables and school variables as predictors of job satisfaction. Self-efficacy, control of classroom discipline, age, gender, years of work experience at the current school, and employment status are personal factors that explain teacher job satisfaction. Among the institutional factors, the important effect of teacher-student relations stands out.