Three cases of patients with synchronous multiple thymoma are reported. Two patients had two thymomas each and the remaining patient had three. The thymomas in each patient all displayed similar histological findings, of which the WHO histological classification were type B2, A and B1, respectively. With a modified Masaoka staging system, the thymomas were determined to be stages II-1 and I in patient 1, one of stage III and two of stage I in patient 2, and two of stage II-1 in patient 3. We reviewed nine reported cases of multiple thymoma in which histological findings were provided and discuss whether they developed from multi-centric origin or from intra-thymic metastasis.