Supervisors' feedback can be taken as the most powerful pedagogical tool in thesis writing. However, relatively little is known about the type of information supervisors focus on and the language functions supervisors use to communicate with their students. Data collected from eight supervisors' written feedback to students' theses at Bahir Dar University, Ethiopia were coded, tabled, and converted into percentages for analysis. The results of this study showed a wide range of supervisors' practices concerning the functions and types of written feedback. While the supervisors favored feedback on the genre knowledge the most and directive clarification language functions was most frequently used to communicate with the students, little or no attention was given for the expressive approval of language functions. Overall, the results of this study suggest that supervisors' written feedback can be taken together in regard to the process of effective communication. Finally, implications for better supervision practices and further research are presented that could shed light on the strengths of using other research tools.