Many teachers today are encouraged to adopt new practices that acknowledge both the art and the science of teaching and to enhance their professional development. One of those practices is the peer coaching process. The purpose of this study was to examine the impact of peer coaching on the professional development of teachers and to survey the attitudes of the participants toward the approach as compared to those of conventional supervision model in in-service TEFL teacher education in Iran. The participants were 20 English teachers of a secondary school in Tehran. They were randomly assigned into two groups: peer coaching program and the faculty supervision program. To measure teacher\'s professional development, Metcalf\'s Clarity Skills were mainly taken into account. For the purpose of the study a pretest-posttest control group design along with two main qualitative research strategies, interview and observation, were used. The blending of data collection methods provided the opportunity to triangulate the data to obtain more reliable results. The findings showed statistically significant differences in favor of the peer coaching group on the variable measured. Furthermore, they demonstrated that, among the participants, there was greater satisfaction with the peer coaching program rather than with the conventional supervision model.