Quality of tuberculosis (TB) microscopy diagnosis is not a guarantee despite implementation of external quality assurance (EQA) services in all laboratories of health facilities. Hence, we aimed at evaluating the technical quality and the findings of sputum smear microscopy for acid fast bacilli (AFB) at health centers in Hararge Zone, Oromia Region, Ethiopia. Of the total 55 health center laboratories assessed during the study period (July 2014-July 2015), 20 (36.4%) had major technical errors; 13 (23.6%) had 15 false negative results and 17 (30.9%) had 22 false positive results. The quality of AFB smear microscopy reading and smearing was low in most of the laboratories of the health centers. Therefore, it is essential to strength the EQA program through building the capacity of laboratory professionals.