The current study targeted at enhancing EFL oral communication skills and self-efficacy of the first secondary stage students through the mastery learning-based strategy. To achieve the purpose of this study, the researcher adopted the quasi- experimental design. The study participants involved (60) students from the first year secondary stage students from Al-Ibrahimia Mixed Secondary School, Al-Ibrahimia Directorate, Sharkia Governorate, Egypt. They were randomly allocated in two groups. A number of (30) students represented the study participants in the experimental group and (30) students for the control group. The study was conducted over a period of (6) weeks, along (15) sessions from “New Hello Book" assigned for the first year secondary stage students over the second semester of the academic year (2019/2020). To gather data, the researcher designed four instruments represented in;  a checklist of the most appropriate EFL oral communication skills necessary for the first year secondary stage students, an EFL oral communication skills test, a rubric to score the test, and a five-point Likert scale for measuring the effect of the mastery learning-based strategy on the students' self-efficacy. These instruments were submitted to a panel of EFL jury members to check their validity. These instruments were administrated before and after the treatment to both the experimental and control groups. Data were collected and analyzed statistically. The results revealed that there is a statistically significant difference between the mean scores of the experimental group and that of the control group in their oral communication skills and self-efficacy in favor of the experimental group. Findings of the current study were ascribed to the mastery learning-based strategy that provided evidence for its positive effect on enhancing the first year secondary stage students and on their self-efficacy. In the light of these findings, some relevant recommendations and suggestions for further research were