This study delves into the correlation between the beliefs of five university mathematics teachers regarding the teaching of mathematics and their instructional practices. Adopting a case study methodology, this research aimed to thoroughly investigate this relationship. The collection of data was carried out through questionnaires, and the analysis was performed using IBM SPSS Statistics 20. The results indicate that the beliefs held by teachers significantly influence their instructional practices. Teachers with a belief in the transmission model of teaching mathematics are more inclined towards teacher-centered methodologies, whereas those who subscribe to a discovery or connectionist perspective favor student-centered approaches. Moreover, a clear relationship was found between teachers' beliefs concerning the nature of mathematics, its teaching methodology, and the learning process, and their instructional practices. Recognizing the importance of teachers' beliefs about the teaching and learning of mathematics is essential, as these beliefs profoundly affect instructional practices. It is suggested that teacher education and ongoing professional development programs should focus on modifying beliefs regarding mathematics and its learning processes to enhance instructional practices. Continuous professional development interventions aimed at refining these beliefs could lead to improved outcomes for students.