IL-17 and IL-17-producing cells have been found in many types of human cancers and murine models. However, the source of tumor-infiltrating IL-17 and IL-17-producing cells in HCC and the prognostic values remain poorly understood. A total of 57 HCC patients were enrolled in this study, and immunofluorescence double stain was used to evaluate the colocalization of CD3 T cells, CD4 T cells, CD56 NK cells, CD20 B cells, CD68 Macrophages, and MCT mast cells with IL-17. The prognostic value of IL-17-producing cells was evaluated by Kaplan-Meier analysis and Cox regression model. MCT mast cells, but not other cells, were the predominant IL-17-producing cell type. Overall survival analysis revealed that the increasing intratumoral-infiltrated MCT mast cells were significantly associated with poor prognosis. Immunofluorescence double stain showed a positive correlation between the number of MCT mast cells and MCVs. These findings indicated the major IL-17-producing cells in HCC were MCT mast cells and these cells infiltration may promote tumor progression by angiogenesis. Increased MCT mast cells was associated with a poor prognosis, indicating therapy targeting MCT mast cells might be an effective strategy in controlling intratumor IL-17 infiltration and MCVs.