The purpose of this study was to assess factors leading students to absenteeism in Secondary Schools of West Wollega Zone. In this study survey research method was employed; and descriptive statistics to analyze the data i.e. frequency and percentage, were adopted. To assess the extent of absenteeism and its causes in secondary schools, questionnaires were administered for the three selected secondary schools of West Wollega Zone. There were 474 participants, including 105 teachers and 369 students and also interview were held with three principals and five vice principals. The results of interviews were analyzed and integrated with the results of questionnaires to support the findings of the study. Totally, 482 respondents participated in this study. To consolidate the findings document analysis was also made. The three selected schools attendance was collected from both grade nine and ten. Moreover, the results GPA for grade ten and roster for grade nine students were seen. According to the results, absenteeism greatly affected studentsâ€™academic achievement. This means the absent students achievement was very poor when compared to regularly attending students. Generally, family related problem, environment, school factors and personal factors triggered student absenteeism in the studied schools and the effects of absenteeism was shown by 86.4% of the respondents. This shows that absenteeism inversely related to academic achievement. The study also recommended that the school communities, concerned government officials and all stake holders need to be aware of the seriousness of students absenteeism and its impacts.