This study has examined the development of students' writing performance and writing self-efficacy in an EFL flipped course designed with teacher's beliefs and perceptions. In so doing, a total number of 60 English language department students were randomly assigned to be EFL participants of this quasi-experimental design, the researcher utilized an experimental group that received flipped writing instruction model which is characterized by teacher's beliefs and perceptions and a control group that received regular instruction model only for three months. The Academic writing test(AWT) and the Writing Self-Efficacy Questionnaire (WSEQ) were administered to measure the writing skills and self-efficacy of the participants. The results of the study revealed that the students in the flipped teacher's beliefs group substantially performed better than those of the non-flipped group regarding both writing achievement and writing self-efficacy. To conclude, EFL educators can positively incorporate flipped instruction into their writing classrooms in order to scaffold students to gain both confidence and competence in doing writing tasks more properly. Furthermore, flipped instruction contributes to establishing a highly motivated learning context when EFL teachers' perceptions match hormonally with