CD3+/CD57+ T-cell large granular lymphocyte leukemia (T-LGLL) is an indolent neoplasm, exhibiting mostly CD8+, less frequently CD4+ phenotypes, and T-LGLL consisting of 2 populations with CD8+ and CD4+ phenotypes is markedly rare. An 87-year-old female was admitted under a diagnosis of immune thrombocytopenia (ITP) with a platelet count of 5.0×109/L and increased number of LGL with unknown etiology. Her neutrophil count also decreased to 0.27×109/L and she was positive for antineutrophil antibody. The WBC count was 2.7×109/L with 34.7% LGL and flow cytometry (FCM) analysis revealed 16% CD3+/CD4+/CD8dim/CD57+ and 20.9% CD3+/CD8+/CD57+ populations. These populations also expressed granzyme B and perforin. Circulating mononuclear cells were found to be clonal by PCR analysis of T-cell receptor β-chain gene. Serum immunofixation and bone marrow FCM analyses demonstrated 2 clonal B-cells producing IgG-λ and IgA-λ. Deep amplicon sequencing of STAT3 and STAT5B genes revealed a STAT3 R302G mutation with an allele burden of 2.6%. The thrombocytopenia and neutropenia were successfully treated by prednisolone and romiplostim with negative conversion of antineutrophil antibody. This is the first reported case of T-LGLL with dual components of CD4+/CD8dim and CD4-/CD8+ populations in terms of multiple comorbidities related to the respective CD8+ and CD4+ T-LGLLs.