In the study, it is aimed to investigate the student, teacher and school factors predicting mathematics achievement of Turkish 8th grade students in TIMSS 2015. The group of the study consists of 6079 students and 220 teachers who attended TIMSS from Turkey. The data of the study was obtained from student and teacher questionnaires and mathematics cognitive test scores. In the data analysis, multilevel regression analysis was used in which dependent variables were plausible mathematics scores and independent variables were student, teacher and school scale scores. According to results, 34% percent of student-level variance was explained by student-level variables. It was found that self-confidence level of students was the most important predictor of mathematics achievement among student-level variables. Additionally, educational resources at home variable was also among the important predictors of mathematics achievement. Teacher and school factors explained 29% of between school variance. Among these variables, school emphasis on academic success and teaching limited by student needs were two significant variables that could predict mathematics achievement of students.