Specification began with the inclusion of the primary exogenous predictorvariable number sense and the endogenous outcome variables of mathematics selfconceptand mathematics achievement. As an indicator of number sense, highest91proficiency level mastered detailed skill level based on clusters of questions includingnumber sense items. The perceived interest and competence in mathematics score,derived from Marsh’s Student Descriptive Questionnaire II, was utilized as a measure ofmathematics self-concept. Finally, the mathematics teacher academic rating scale waschosen to represent mathematics achievement. Directionality presumed causal effectsfrom number sense to both mathematics achievement and mathematics self-concept, andfrom mathematics self-concept to mathematics achievement. The paths from numbersense to mathematics achievement and mathematics self-concept corresponded to the firsttwo research hypotheses stating that number sense predicts both mathematicsachievement and mathematics self-concept. With the additional path from mathematicsself-concept to mathematics achievement, the third research hypothesis is represented,asserting that mathematics self-concept mediates the path from number sense tomathematics achievement.