To help learners acquire and develop the necessary skills for the 21st century, Algeria has adopted the Competency-Based Approach (CBA) along with the Project-based Learning (PBL) approach within its educational system. Theoretically speaking, the goal behind such reform is to shift from a content-based to a process-based learning/teaching and thus to make learning more relevant and realistic for students. However, in practice, teachers find difficulties in putting into practice the two approaches. The aim of the present paper is to explore those obstacles that hinder the execution of the PBL approach in the third-year secondary education English classes and to identify to what extent English language teachers master and use PBL methodology in their classes. To reach the aim of the study, the following hypothesis is put forward: teachers lack both training and background knowledge on the approaches that help to implement PBL in classrooms. For the sake of collecting information about the issue tackled in this study, twenty EFL teachers from some secondary schools in Mostaganem city received a questionnaire. The research findings confirm the hypothesis mentioned above. They reveal that teachers neither master nor use the project-based instruction proficiently in their classrooms despite the guidance provided in the third-year pedagogical documents. Those hindrances are due to the lack of professional training and the insufficient theoretical knowledge on the diverse approaches, methods and strategies related to PBL.