Abstract The purpose of this research was to investigate the effect of using a situated instructional coaching web-based program to develop EFL in-service teachers' teaching skills and their self-efficacy. To fulfill the purpose of the study, four instruments were prepared. First, a Teaching Skills Questionnaire was used to identifying the teaching skills that EFL in-service teachers in government schools would need to develop. Second, a pre-post Teacher's Knowledge Test was used for assessing the teaching skills of the EFL in-service teachers, using an answer key for scoring teachers' answers was developed. Third, a Teaching Skills Observation Checklist was used to assess the EFL in-service teachers' classroom performance regarding the selected teaching skills under investigation. Fourth, a Self-Efficacy Scale was used to measure teachers' level of efficacy in teaching before and after implementing the situated instructional coaching program. The study adopted the quasi-experimental pre-post test one group research design. The participants were one group of EFL in-service teachers (N= 20) selected from government schools. Results revealed that there was a statistically significant difference between the mean ranks of the treatment group on both the pre and post-administrations of the teacher's knowledge Test in favor of the post-administration. Also, there was a statistically significant difference between the mean ranks of the treatment group on both the pre and post-administrations of the Teaching Skills Observation Checklist in favor of the post-administration. Finally, there was a statistically significant difference between the mean ranks of the treatment group on both the pre and post-administrations of the Self-Efficacy Scale in favor of the post-administration. These results showed that the situated instructional coaching web-based program was effective in developing EFL in-service teachers' teaching skills and their Self-Efficacy. Key Words: Situated Instructional Coaching, Web-Based Program, EFL In-Service Teachers, Teaching Skills, Self-Efficac