Professional ethics in medical laboratory is important and extensive. It comprises trustworthy and valued conducts of professionals against public and patient. Medical laboratory professionals need education and training to exhibit ethical conducts. Teaching professional ethics may change ethical knowledge, attitude and conduct of healthcare professionals. Ethics education is done in different ways. Lecturing is a common method to teach ethics. Lecturing method is based on theoretical concepts. This study has been designed and conducted to assess the effect of teaching professional ethics on ethical knowledge and attitude, by using questionnaire on 24 medical laboratory staff. Result showed that, teaching ethics by lecturing method increases ethical knowledge and improves attitude of medical laboratory staff.