The main purpose of the current study was to investigate the impact of a program based on Web2 Applications in developing 70 randomly selected EFL secondary school students' writing self-efficacy from El- SayedaKhadega Secondary School for Girls in Zagazig, Sharkia  Governorate in the first semester of the academic year 2018/2019. The sample of the study was equally divided into the experimental and control groups. To achieve the purpose of the study, the researcher developed the EFL writing self-efficacy. The program based on the Web2 Applications was designed and administered by the researcher for teaching the students in the experimental group whereas the students of the control group were taught by the regular method. The results of the study revealed that the program based on the Web2 Applications is significantly effective in developing the experimental group students' writing self-efficacy. Besides, the students in the experimental group outperformed their peers in the control group, who received the regular instruction, on the EFL writing self-efficacyscale. These results confirmed on the importance of integrating Web 2.0 applications in the EFL classroom for developing EFL students' writing self-efficacy.