Background: Clinical trials evaluating immune checkpoint inhibition (ICI) in recurrent high-grade gliomas (rHGG) report 7-20% 6-month progression-free survival (PFS), while re-irradiation demonstrates 28%-39% 6-month PFS. Aims: We evaluate outcomes of patients treated with ICI and concurrent re-irradiation utilizing stereotactic body radiotherapy / fractionated stereotactic radiosurgery (SBRT) compared to ICI monotherapy. Methods and Results: Patients >18-years-old with rHGG (WHO grade III and IV) receiving ICI+SBRT or ICI monotherapy between 1/1/16-1/1/19 were included. Adverse events, 6-month PFS and overall survival (OS) were assessed. Log-rank tests were used to evaluate PFS and OS. Histogram analyses of apparent diffusion coefficient maps and dynamic contrast-enhanced magnetic resonance perfusion metrics were performed. Twenty-one patients with rHGG (ICI+SBRT: 16; ICI: 5) were included. The ICI+SBRT and ICI groups received a mean 7.25 and 6.2 ICI cycles, respectively. There were five grade 1, one grade 2 and no grade 3-5 AEs in the ICI+SBRT group, and four grade 1 and no grade 2-5 AEs in the ICI group. Median PFS was 2.85 and 1 month for the ICI+SBRT and ICI groups; median OS was 7 and 6 months among ICI+SBRT and ICI groups, respectively. There were significant differences in pre- and post-treatment tumor volume in the cohort (12.35 vs. 20.51; p=0.03), but not between treatment groups. Conclusions: In this heavily pretreated cohort, ICI with re-irradiation utilizing SBRT was well tolerated. Prospective studies are warranted to evaluate potential therapeutic benefits to re-irradiation with ICI+SBRT in rHGG.