This study explored the effects of teacher commitment on student achievement. Three teacher commitment dimensions of organizational, professional, and student commitment were derived. The three-dimensional teacher commitment measurement model was tested by a confirmatory factor analysis. Then, the relationships among individual and organizational variables, teacher commitment, and student achievement were analyzed by a 2-level hierarchical linear modeling method. As the results, the greater portions of teacher commitment and student achievement variances were within schools. The individual and organizational variables had differential impacts on each teacher commitment dimension. Finally, while teacher commitment effects on student achievement were differentially found depending on teacher commitment dimensions at the individual level, there was no evidence to support significant impacts of teacher commitment on student achievement at the organizational level.