High-grade glioma is a malignant tumour; the pathogenesis is to be further investigated. Interleukin (IL)-17 is an inflammatory cytokine. Chronic inflammation is a pathological feature of cancer. This study aimed to characterize the glioma-derived IL-17+ regulatory T cells (Treg). In this study, single cells were isolated from surgically removed high-grade glioma tissue and examined by flow cytometry. The immune suppressor effect of IL-17+ Tregs on CD8+ T cells was assessed in vitro. The results showed that abundant IL-17+ Tregs were found in high-grade glioma tissue. The immune suppressor molecule, transforming growth factor (TGF)-beta, was detected in the IL-17+ Tregs. The proliferation of CD8+ T cells was suppressed by culturing with the IL-17+ Tregs, which was partially abrogated by neutralizing antibodies of either TGF-beta or IL-17 and completely abrogated by neutralizing antibodies against both TGF-beta and IL-17. In conclusion, IL-17+ Tregs exist in the high-grade glioma tissue; this subset of T cells can suppress CD8+ T cell activities via releasing TGF-beta and IL-17.