The purpose of this study was to assess the implementation of active learning approach in mathematics class. In order to achieve this purpose, the researcher employed descriptive design using mixed research methods. From the total population of 46 preparatory mathematics teachers and 469 ( ) Grade 11 students of the sampled schools in Bale Zone, the study was conducted on a sample of 23 teachers and 100 students which were selected systematically. The data were collected through questionnaire for both teachers and students, interview for teachers and class observation. A questionnaire was administered to 23 teachers and 100 students which were systematically selected. Besides, an interview and classroom observation was conducted to get some insight in to the implementation of active learning approach in mathematics classes. The obtained data was analyzed both qualitatively and quantitatively. A quantitative analysis was carried out on teachers’ and students response to the closed –ended questionnaires. The data obtained through interview and class observations was analyzed qualitatively. Accordingly, the overall findings of this study showed that the implementation of active learning approach was found to be unsatisfactory. The teachers dominantly used lecture method which was traditional method. Active learning approaches like: pair work, debate, problem solving, drama and games, brainstorming, peer teaching and group discussion were not practiced at all. Furthermore the study found out that lack of students’ interest, large class size, textbook’ broad content, lack of teachers’ training and support on the implementation of active learning, shortage of time, work load of teachers and teachers less commitment were the major factors to hamper the implementation of active learning. Therefore, the researcher recommends that great emphasis should be given to these factors by all stakeholders in assuring the quality of education.it is very important to give emphasis and work upon these factors by all concerning bodies to assure the implementation of active learning .4