Faculty members are engaging with three important roles at university including teaching, research and services. However, the main focus of higher education on research has caused the neglect of teaching among faculty members. This is resulted in lack of information about what and how to develop teaching knowledge in different higher education disciplines. As well, teaching knowledge is practical in nature and that, contributed to the complexity of its study. Among different models, pedagogical content knowledge (PCK) model was chosen to study the nature of mathematics instructors’ teaching knowledge at higher education level. The data were collected through semi-structured interviews, with a number of university mathematics instructors. The data were analyzed using phenomenology. The analysis revealed that university mathematics teachers develop their pedagogical content knowledge, through some resources including model making, repeating courses, mathematics textbooks, students, colleagues, and their prior experiences as student, educational resources and mentoring. Moreover, the direction of PCK development is from content to learner and considering these resources towards the development of PCK, yet needs another factor as reflection on action, is influencial.