Background: Myasthenia gravis (MG) is an autoimmune disease affecting acetylcholine postsynaptic receptor of voluntary muscles. Thymectomy is done in these patients and is a mainstay in the treatment of MG; however, the long-term result of surgery is still controversial. This study dealt with the investigation of the results of thymectomy in treatment, recovery and control of the symptoms of these patients.Methods: This study was performed through a retrospective method in patients suffering from MG who underwent trans-sternal thymectomy between 2011 and 2016. We conducted thymectomy, excision of mediastinal mass and contents of tissues between the right and left phrenic nerves for all patients. Then, the effect of various variables including age, sex, time interval between onset of disease and surgery, thymus pathology and the dosage of drug on clinical response after surgery was determined using various statistical tests.Results: 47 patients including 26 men and 21 women with the mean age of 33.0 ± 4.6 years have been investigated. The mean age of patients was 36.2 and 29.7 in men and women respectively (P = 0.041). Spiral chest computed tomography (CT) scan was present in 47 patients demonstrating mediastinal mass in 40 (85.1%) patients. Also, our pathological results showed thymic cells in aortopulmonary window contents of 4 patients. According to the results, the younger age of patients at the time of surgery, shorter time between diagnosis and thymectomy, being a woman and non-thymoma pathology were along with better clinical outcomes after thymectomy.Conclusion: Our study shows better clinical results of thymectomy in patients with normal chest CT scan and normal or atrophic thymus in pathologic reports. Generally, it seems that performing thymectomy in a shorter time interval after diagnosis of MG is beneficial. Moreover, in MG patients who do not suffer from thymoma, it is along with positive results.