Medical error is the failure of a planned action to be completed as intended or the use of an incorrect plan to achieve the goal. Competent error disclosure is an important opportunity to develop trust and loyalty between the patient-society-physician. The main reason for the competent error disclosure is to protect the public's trust in the medical profession. In most cases of medical error, the state of silence, almost collusion with each other, to cover up the error, can be considered as an illegitimate and problematic element of the medical culture. No matter how insignificant or serious the medical error that occurs in ethical codes and professional guidelines, it has been clearly demonstrated that the physician has the responsibility to inform the patient by explaining this error. It is an ethical obligation of the physician to explain each medical error situation to the patient. Available data show that the number of medical errors that occur during radiation therapy is substantial. However, there are limited studies focusing on the tendency of radiation oncologists to report medical errors. In this study, we would try to emphasize the importance of the disclosure of medical error in radiation oncology by considering its ethical dimensions.