The purpose of this study was to assess the practices and challenges of school based supervision in public primary schools in Oromia National Regional State, Ethiopia. Descriptive survey research design was employed to carry out the study. The study participants were 147 respondents (75 instructional leaders and 72 teachers who were selected by using simple random and purposive sampling techniques respectively).An investigators adopted descriptive and inferential statistics to make interpretation of quantitative data sound whereas qualitative data were analyzed thematically to substantiate quantitative data. The results of the study indicated that the practices of school basedsupervision wasconducted sometimes due to shortage of time, limited input physical resources, negative attitudes of the teachers toward instructional supervision, and lack of commitment from both instructional leaders and teachers. It is suggested that educational officials and school community should give due attention to the school based supervision to improve the practice of school based supervision which resulted in students achievement.