The purpose of this study was to assess the practices of school-based supervision in government secondary schools of Genji Woreda West Wollega Zone. One Zonal and one Woreda Education Office supervision coordinators were selected through purposive sampling technique. Among the 5 government secondary schools found in the woreda, 4 of them were selected randomly as sample schools. From these sample schools, 10 principals (vice principal) and 2 school-based supervisors (4 unit leaders and 16 heads of department) were also included as respondents using purposive sampling technique. Furthermore, 60 teachers have participated in the study through systematic sampling technique. Questionnaire was used as main tool of data collection. Interview and document analysis were used to substantiate the data gathered through questionnaires. Frequency, percentage, mean and t-test were utilized to analyze quantitative data gained through the questionnaires. The qualitative data gathered thorough interview and document analysis were by narration. Likert scales is going to be employed, because Likert scale is the simplest way to describe opinion. The scale consists of five scales. Scales; ≤ 1.49 = very low, 1.5 – 2.49 =low, 2.5 – 3.49 = moderate, 3.5 –4.49 = high , ≥ 4.5 = very high. The result of the study indicated that teachers lack awareness and orientation on the activities and significance of school-based supervision, ineffectiveness of the practices of supervisory options matching with the individual teacher’s developmental level, and inability of supervisors to apply the necessary procedures for classroom observation properly. School-Based Supervision(SBS):- Is important for monitoring the quality of education and its consequences in ensuring the effective and efficient outcome of the school. On the other hand, among the factors influencing the school-based supervision, lack of relevant training programs for supervisors, scarcity of experienced supervisors in school-based supervision activities, lack of supervision manuals in the schools and shortage of allocated budget for supervisory activities. Therefore, it is possible to conclude that teachers were not motivated at work through the implementation of various supervisory options. Thus, the contribution of supervisory options for teachers’ professional development and the improvement of instruction was insignificant. Teachers couldn’t get the maximum supports from school-based supervisors. Therefore, the teaching and learning process was not enriched by well supported teachers‟ professional development. Finally, to minimize the problems of school-based supervision in secondary schools, it is recommended to give relevant in-service trainings for supervisors to upgrade their supervisory activities, necessary resources such as supervision manuals and an adequate budget for the success of supervision at the school level was suggested.