This study investigated effect of student- and school-level variables on mathematics achievement of fourth- and eighth-grade students using the Trends in International Mathematics and Science Study (TIMSS) 2011 data of Turkey. The common variables addressed in student and school questionnaires were compared. Due to nested structure of the TIMSS data, hierarchical linear modeling analysis was performed. According to findings of the study, for both grade levels, of all teacher-related variables, only school emphasis on academic success were discovered to have statistically significant impact on schools' mean mathematics achievements. Moreover, concerning student-level variables, being bullied at school, confidence in mathematics, being engaged in mathematics and parental involvement had statistically significant effect on students' mathematics achievement for both grade levels. It is considered that students that hold more positive perceptions of their school and have teachers that are willing to improve themselves in their career tend to have higher performance in TIMSS. [This study was presented at the 10th International Test Commission (ITC) Conference in 1-4 July 2016 in Vancouver, Canada.]