This study was conducted in Dire-Dawa University on instructors 'rnparticipation in Teacher Development Program (TDP). To investigate thernnature of instructors' participation in TDP five basic questions werernformulated. Proportional stratified sampling and purposive samplingrntechniques were employed to take samples from the total population. Torngather relevant information questionnaire (75 instructors), interview (4-rninstructors, 6-management, and 3-TDP staff) and document analysis werernused. Then after, the gathered data were analyzed quantitatively andrnqualitatively by using concurrent nested strategy (mixed method). Amongrnthe quantitative methods, inferential and descriptive methods were used.rnThe qualitative data were analyzed after collected and categorized.rnFindings of this research show that, the instructors were participating inrnfew areas; they have benefited from their participation in the availablernareas of TDP, and the competence of the program facilitators was foundrnsatisfactory with some limitations, such as, integrating the discussion withrncurrent research out puts and the immediate environment where they canrnbe put in to practice and finally the role of the university management wasrnfound unsatisfactory. Instructors were found participating regardless ofrntheir pedagogical background and there was no statistically significantrndifference in getting help across schools in the university fromrnparticipation. In order to get the desired contribution from the programrnsuch recommendations as the program should be led by individuals whornare professionally and academically competent, the instructors should berncommitted for the progress of their own profession, and the UM shouldrnchange their attitude towards the program were made.