Observation and self-awareness are key ingredients to all work involving people. Especially classroom observation makes teaching and learning more visible. It encourages colleagues to collaborate to improve teacher practice and student learning. In this realm, we present in the following article the results of such a case among two teachers (an observer and a teacher being observed) of a Greek Experimental High School. Τhe observation’s purpose was to provide feedback on teaching practices and to suggest ways to improve those practices, if appropriate. Aiming at the validity of the observation the procedure was recorded whereas apart from the observation of the class session, both a pre- and post-observation conference was set up. The results highlight the importance of peer observation in shaping a supportive and developmental process for improving the quality of educational process.