Epistemic beliefs are individual’s beliefs about the nature of knowledge and knowing, as well as an important predictor of the learning process and outcome. The aim of this research was to explore the relationship of epistemic beliefs with achievement goals and approaches to learning mathematics at the university level, and to determine whether achievement goals have a mediating role in the relationship between epistemic beliefs and student approaches to learning mathematics. Two aspects of epistemic beliefs were explored - the maladaptive belief about simple knowledge and the adaptive belief about knowledge justification. The dimension of simple knowledge refers to the concept of knowledge as a continuum with the accumulation of facts on one side, and the concept of knowledge as highly connected and interdependent concepts on the other, while the justification dimension refers to beliefs on how different information can be verified, including practical application and proving. The participants were 333 first-year students of electrical engineering and computer science. They completed scales of their epistemic beliefs, achievement goals, and student approaches to learning, all related to the mathematics course. The results show that epistemic beliefs are negatively, and beliefs about justification, positively related to effective motivational and cognitive processes during learning. Also, in line with the hierarchical model of achievement goals, they represent significant mediators of the relationship between epistemic beliefs and students’ approach to learning mathematics. Therefore, it is important that teachers encourage adaptive epistemic beliefs by promoting the value of understanding theory and by encouraging the integration and practical application of acquired knowledge.