The objective of the study is to assess factors affecting teachers’ performance appraisal practices of South West Shewa zone public secondary schools. This study designed both quantitative and qualitative data gathering techniques with descriptive analysis and interpretation techniques. The study was conducted in 6 secondary schools from among 27 public secondary schools. This study used 226 teachers, 6 principals, 6 vice principals and 24 department heads by giving equal chances for six sampled school when conducting questionnaire and interview. Simple random sampling technique was used to select cluster and teachers.The availability sampling technique used to select representative principals and department heads. In order to do this four data gathering tools were applied; those are, questionnaire, interview, focus group discussion and document analysis. Quantitative data was analyzed using descriptive statistics; percentages and means. The major findings of the study revealed that there was no participation of teachers in establishing appraisal criteria and standards, there wasn’t gathering multiple sources of evidences from various groups about teachers performance during appraisal time, school designed practice was not to encourage formative assessment, many factors hinder TPA like absence of reward, lack the necessary knowledge of appraisers, lack of required skill and appraisers biases had appeared. To undertake effective teachers’ performance appraisal, the school should allow and encourage teachers’ participation in the entire process of performance appraisal starting from the initial meeting to post appraisal conference through increasing open discussion, mutual agreement and common understanding on a plan of action, also there should be all sided or 360 degree when gathering information about teachers’ performance appraisal, unless the appraiser and teachers’ perceive adequate knowledge on the purpose of performance appraisal, the intended goal will not be achieved, Therefore, the South West Shewa Zone education office, each woreda education office and the schools are expected to make maximum effort to give consistence solution concerning the raised problem.