The approximate number system (ANS) is frequently considered to be a foundation for the acquisition of uniquely human symbolic numerical capabilities. However, the mechanism by which the ANS influences symbolic number representations and mathematical thought remains poorly understood. Here, we tested the relation between ANS acuity, cardinal number knowledge, approximate arithmetic, and symbolic math achievement in a one-year longitudinal investigation of preschoolers’ early math abilities. Our results suggest that cardinal number knowledge is an intermediary factor in the relation between ANS acuity and symbolic math achievement. Furthermore, approximate arithmetic performance contributes unique variance to math achievement that is not accounted for by ANS acuity. These findings suggest that there are multiple routes by which the ANS influences math achievement. Therefore, interventions targeting both the precision and manipulability of the ANS may prove to be more beneficial for improving mathematical reasoning compared to interventions targeting only one of these factors.