Medication errors (ME)areamong the most common medical errors.Their reporting is an integral part of health care quality improvement.Therefore, this cross–sectional study examinedthe knowledge and barriers to reporting of ME amongphysicians in primary health carecenters in Al–Khobar, Qatif, and Dammam in Eastern Province, Saudi Arabia. A structured questionnaire was administered to 220 physicians(71% response rate).Only 14.5 % of the participants had good knowledge ofME; 69.1% were unaware of their center’s ME reporting system. In terms of barriers to reporting, 59.1% of the participants reported heavyworkload as a barrier.Such major gaps in knowledge ofME and their reporting system indicate the need for educational programs and to address thebarriers to increase reporting rate.