In this study, the Trends in International Mathematics and Science Study 2007 data were used to build mathematics achievement models of fourth graders in two East Asian school systems: Hong Kong and Singapore. In each school system, eight variables at student level and nine variables at school/class level were incorporated to build an achievement model through hierarchical linear modelling. The final achievement models suggested that in both school systems, four variables at student level, i.e. number of books at home, frequency of test language spoken at home, frequency of mathematics homework, student's self-confidence in learning mathematics, and one variables at school/class level, i.e. class size for mathematics instruction were significantly correlated with fourth graders' mathematics achievement, and student's self-confidence in learning mathematics was the strongest predictor of mathematics achievement. The relations between mathematics achievement and other variables differed across the two systems. Implications for educational research and practice are presented at the end of this paper.