Type AB thymoma is a thymic epithelial neoplasm composed of component spindle cell (type A) and lymphocyte-rich (type B) component. An exceptional atypical type A thymoma variant with uncertain prognosis was added to the WHO classification of thymomas in 2015. We report a case of a 62 years old man presented with clinical myasthenia. The radiological examination revealed a well-circumscribed anterior mediastinal mass. The patient underwent complete thymectomy. Pathological and immunohistochemical analysis revealed an AB thymoma with atypical component of type A. At the first year post surgery follow-up appointment, the patient was alive with no evidence of recurrence or complication. The presence of atypical component of type A thymoma may increase the risk of progression or metastasis, so extended follow-up for patients is required