The object of this study was to analyze treatment outcomes and to identify the prognostic factors, with a focus on the role of adjuvant radiotherapy (ART), predicting disease progression in atypical meningiomas. From 1997 to 2011, 83 patients with meningioma were included in this study. All patients were histologically confirmed as atypical meningioma and were treated with surgical resection with or without ART. As primary therapy, 27 patients received surgical resection followed by ART, and 56 received no adjuvant therapy. Of 83 evaluable patients, 55 (66.3 %) patients underwent complete resection. The median ART dose was 61.2 Gy and their median age was 52 years. The 5- and 10-year actuarial overall survival rates were 90.2 and 62.0 %, and the 5- and 10-year progression-free survival (PFS) rates were both 48.0 %, with a median follow-up of 43.0 months. Addition of ART (p = 0.016) and complete tumor resection (p = 0.002) were associated with superior PFS. When stratified to four groups according to resection status and ART, the groups of patient with incomplete resection without ART showed significantly worse PFS compared to other three groups (p < 0.001). In conclusion, surgical resection followed by ART led to lower local tumor progression in patients with atypical meningioma defined by the updated 2000/2007 WHO classification. Our results may contribute to the routine use of ART, especially after incomplete resection, until the outcomes of ongoing prospective trials are available.