This study examined the relationship between mathematics achievement and epistemic actions. Cognitive actions that are observed as outcomes of using intellectual resources are referred to as epistemic actions in this study. We focused on four epistemic actions as follows: "selecting," "analyzing," "computing," and "representing," which are theoretically important to understand mathematical practices and required to solve test items. We sequentially applied the generalized DINA (generalized deterministic inputs, noisy "and" gate) and linear regression to the Iowa Assessments data from grades 6 to 8. The findings showed that mastery of the epistemic actions contributed to the improvement of mathematics achievement individually as well as collectively. The actions of "selecting" and "computing" contributed to higher mathematics achievement across grades 6 to 8, while the development of "representing" improved mathematics achievement, though to a lesser degree. Students with all four epistemic actions had considerably higher mathematics achievement compared to their peers with other possible combinations of "selecting," "analyzing," "computing," and "representing." We also found learning loss because of the transition from elementary school to middle school. The findings suggested that students need to be offered more opportunities to experience these epistemic actions collectively with greater instructional emphasis on analyzing patterns and selecting strategies to find correct answers. However, when students have difficulties in the development of epistemic actions, teachers can have different emphasis on "representing" in elementary schools, "selecting" and "analyzing" in middle schools, and "computing" through elementary and middle schools.