The main purpose of the current study was to investigate the impact of a program based on Web2 Applications in developing 70 EFL secondary school students' writing self-efficacy from El- Sayeda Khadega Secondary School for Girls in Zagazig, Sharkia  Governorate in the first semester of the academic year 2018/2019. The participants of the study were equally divided into an experimental and a control group. To achieve the purpose of the study, an EFL writing self-efficacy scale was developed. The program based on the Web2 Applications was designed and administered to the participants in the experimental group whereas the control group was taught by the regular method. The results of the study revealed that the program based on the Web2 Applications was 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-efficacy scale. These results confirmed the importance of integrating Web 2.0 applications in the EFL classroom for developing EFL students' writing self-efficacy