The current study intends to investigate teachers’ beliefs about the issues encountered by writing teachers when they assess writing skills at the University of Algiers2. It also examines the factors which lie behind these challenges. Understanding the nature of the perceived challenges of assessing writing is very important to rethink the assessment practices of writing skills. Therefore, this study addresses the following research question: what are teachers’ beliefs about the issues encountered when assessing students’ writing skills? In this concern, the researcher adopted mixed method research to collect data by using a questionnaire and a semi-structured interview with ten teachers of writing selected randomly in the English department at the University of Algiers 2. Findings revealed that almost all teachers viewed the process of assessing writing as a very challenging task. Examples of the difficulties identified in this research include students’ language problems, teachers’ confusion between focusing on the content or the form, time pressure, overloaded classes, and lack of sufficient time to assess students’ writing skills. Regarding the reasons behind these perceived challenges, teachers believed that the abovementioned issues stemmed from the lack of participation in a professional development program, low teaching load, and students’ lack of intensive practice. This research provided a set of pedagogical implications to overcome these issues by calling for an emphasis on the importance of teachers’ participation in a professional development program, reinforcement of teachers’ training in the field of assessment, and the encouragement of students’ intensive practice, and a sufficient teaching load.