Purpose: To evaluate immunophenotypic profiles of infiltrating cells in surgically excised tissues of chalazion and pyogenic granuloma associated with chalazion.Methods: Eighty-two surgical specimens from 74 consecutive patients newly diagnosed with chalazion or chalazion-associated pyogenic granuloma at Tokyo Medical University Hospital between 2016 and 2022 were studied. Sixty specimens were chalazion lesions and 22 specimens were pyogenic granuloma lesions (from 15 men and 7 women, mean age 36.6 ± 14.4 years). All patients were immunocompetent Asian Japanese adults. Specimens were analyzed by immunohistochemistry and flow cytometry. Flow cytometry was performed using the following antibodies: CD3, CD4, CD8, CD11b, CD11c, CD16, CD19, CD20, CD23, CD25, CD34, CD44, CD56, CD69, and CD138.Results: In flow cytometric analysis, the proportion of cells expressing the T cell marker CD3 was significantly higher compared with other immune cells expressing specific markers (p < 0.0001), and the proportion of CD4-positive T cells was significantly higher than that of CD8-positive T cells (p < 0.0001), in both chalazion and pyogenic granuloma specimens. The chalazion and pyogenic granuloma lesions shared similar immunophenotypic profile characterized by predominant T cell infiltration, and CD4 T cells dominating over CD8 cells. The pattern of expression of CD4 and CD8 in the specimens was confirmed by immunohistochemistry.Conclusion: The present study demonstrates immunophenotypic features of chalazion and chalazion-associated pyogenic granuloma. Although various inflammatory cells are involved in the pathology of chalazion and pyogenic granuloma, a significantly higher proportion of CD4-positive T cells may be closely related to the pathological mechanisms of both lesions.