Background Solitary fibrous tumors of the central nervous system are rare and treatment options are not well established. The aim of this study was to evaluate the clinical outcomes of radiotherapy and re-radiotherapy for de novo CNS-SFT and recurrent CNS-SFT.Methods This retrospective analysis included 35 patients (17 female, 18 male) who received RT for CNS-SFT at Heidelberg University Hospital between 2000 and 2020. Efficacy and toxicity of different RT modalities were analyzed in patients who received RT as primary treatment after de novo diagnosis (“primary group”). Of these patients, twelve developed a recurrence which was treated with re-RT (“recurrence group”). Median follow-up period was 54 months (0-282) in the primary group and 20.5 months (0–72) in the recurrence group. RT modalities included 3D-conformal RT, intensity-modulated RT, stereotactic radiosurgery, proton RT, and carbon-ion RT.Results The overall response rate was 40%, with 34% complete remissions and 6% partial remissions in the primary group, and 25% complete remissions and 17% partial remissions in the recurrence group. The 1-, 3-, and 5-year progression-free survival rates were 100%, 96%, and 86%, respectively, in the primary group, and 81%, 14%, and 14%, respectively, in the recurrence group. Proton therapy was associated with a lower likelihood of developing a recurrence in the primary setting than photon therapy (OR = 0.38; p = 0.002), likely due to higher RT-doses (median 60 Gy vs 56.43 Gy). Odds ratio for tumor recurrence was higher for women than for men (OR = 8.07; p = 0.014) with men having a median PFS of 136.3 months, compared to women with 66.2 months.Conclusion The data suggests RT as an effective treatment option for CNS-SFT, with high LPFS and PFS rates. Proton therapy may be associated with a lower risk of recurrence in the primary setting, likely due to the feasibility of higher RT-dose appliance.