The necessity of postoperative radiotherapy (PORT) for meningiomas remains contentious. Here, the role of PORT in patients who underwent surgical resection for WHO grade II and III meningiomas was assessed. The record of 114 patients with WHO grade II (n = 72) and III (n = 42) meningiomas treated at Samsung Medical Center between March 1995 and April 2013 were reviewed and classified according to the extent of surgical resection and implementation of PORT. Median follow-up was 55.9 months. Simpson grade (SG) I, II, III, and IV resections were achieved in 29, 56, 9 and 20 patients, respectively. The 5-year local control (LC) and overall survival rate was 65.8 and 84.2 %, respectively. Thirty patients (26.3 %) developed local failure and five patients (4.4 %) developed distant metastases. The extent of surgical resection (SG I-II vs. III-IV) was influenced by tumor location (orbital and skull base lesions vs. others, p = 0.001) and the surgeons' experience (>10 operations, p = 0.044). Extent of surgical resection was also associated with local failure, overall progression, and overall survival (p = 0.001, p < 0.001, and p < 0.001, respectively). PORT improved LC in patients with incomplete surgical resection (SG III-IV, p = 0.049). Complete resection (SG I-II) is an important prognostic factor for LC and survival, and the extent of surgical resection (SG I-II vs. III-IV) is influenced by tumor location. PORT could improve the LC in WHO grade II-III meningioma patients who underwent incomplete surgical resection (SG III-IV).