In tumor microenvironment, immunosuppression is a common event and results from the inhibition of activated immune cells and generation of cells with immunosuppressive capacity, as some subtypes of monocytes. The aim of this study was to evaluate the presence of immunosuppressive CD14⁺/HLA-DR^low/− monocytes in pediatric patients with the diagnosis of B-cell acute lymphoblastic leukemia (B-ALL) and, moreover, verify whether the chemotherapeutic treatment has any effect on these cells. Peripheral blood (PB) and bone marrow (BM) samples were collected from 15 untreated pediatric patients. The presence of CD14⁺/HLA-DR^low/− monocytes was evaluated at diagnosis and in the end of induction chemotherapy by flow cytometry. CD14⁺/HLA-DR^low/− monocytes increase was observed in 60% (9/15) of the patients at the end of the induction therapy. We were able to detect an increase in CD14⁺/HLA-DR^low/− monocytes values in BM and PB samples of pediatric patients with B-ALL. This increase was observed in the end of induction chemotherapy, which leads us to believe that these changes probably could have been induced by the inflammatory process engendered by the cytotoxic treatment or by drugs used in the chemotherapy treatment. This finding may be useful to guide new therapeutic approaches contemplating immunomodulatory drugs that act in the depletion of immunosuppressive monocytes.