The current study sought to examine whether explicit instruction affects teacher evaluators in terms of a six-factor Teacher Evaluation (TE) model encompassing Perception, Method, System, Content, Purpose, and Outcome. Moreover, it explored how training of the evaluators affects their practices in actual evaluation. To this end, twenty EFL teacher-evaluators selected as the participants of the study filled out a TE questionnaire (developed by the researchers) and participated in a semi-structured interview. In addition, the evaluators' actual practice was examined through recording of post-observation debriefing sessions between the evaluators and the teachers they supervised. Subsequently, a four-session training course on various aspects of teacher evaluation was held. After four weeks, the interviews, questionnaires, and debriefing sessions were repeated. To analyze the data, a two-way repeated measures Analysis of Variance (ANOVA) was run and the comparison of the results showed that the training course had positively affected many aspects of evaluators' perceptions and practices. Likewise, the content analysis of the interviews and debriefing sessions identified the features of the training course that the evaluators found most valuable such as the methods of observation, the strategies required for overcoming the evaluators' communication problems with teachers and managing the debriefing sessions. The results also revealed that the TE factor outcome was not affected by the training instruction course.