Teachers’ further success in and commitment to their profession are shaped by their experiences in the early years of their careers. Being aware of the challenges that novices face would be helpful for teacher-educators in a way that would support pre-service teachers thoroughly. The goal of the current research is to ascertain the perceptions of secondary-school mathematics teachers about the challenging experiences at the beginning of their careers. With this purpose, semi-structured interviews were conducted. Findings revealed several issues that teachers face in four dimensions: mathematical knowledge for teaching, classroom management and organization, assessment of students’ learning, and the context of teaching. Also, teachers’ prior beliefs and expectations showed a general lack of awareness, oversimplified beliefs, and unrealistic optimism about the teaching profession. The findings of this study have shown a deficiency in teacher-education programs in terms of not providing pre-service teachers with enough knowledge of the challenges they may encounter, naturally resulting in the inability to reflect on the various reasons for those challenges and how all four aspects of teaching interact with one another. Regarding the findings, teacher education policies should be refined to help pre-service teachers to develop a more realistic and holistic view of teaching mathematics.