Background and Aim. We studied through flow cytometry the expression of CD146 on different T cells, and B-cell ALL blasts trying to correlate its expression with different prognostic factors of B-cell ALL and treatment outcomes. Patients and Methods. All pediatric patients with B-cell ALL were subjected to bone marrow examination and cytochemistry, flow cytometric immunophenotyping using monoclonal antibodies utilized for diagnosis of B- ALL including CD34, CD19, CD10, CD22, and intracellular IgM. The diagnosis was based on standard morphologic, cytochemical, and immunophenotypic followed by flow cytometric detection of CD146 expression on blast cells, [CD4.sup.+], and [CD8.sup.+] T cells. Results. Significant accumulations of [CD146.sup.+][CD4.sup.+] cells, [CD146.sup.+][CD8.sup.+] cells, [CD4.sup.+], [CD8.sup.+], and lymphocytes in patients were compared to controls, the mean percentages of [CD146.sup.+][CD4.sup.+] cells, [CD146.sup.+][CD8.sup.+] cells, and [CD146.sup.+] blasts were significantly higher in patients than controls, and in addition, these cells were associated with poor overall survival and disease-free survival. The median OS for patients with complete response was 22 [+ or -] 1.633 (95%CI = 18.799-25.201), while for those without complete response, it was 13 [+ or -] 3.928 (95%CI = 5.301-25.699), with log-rank = 5.71, P = 0.017. Conclusion. CD146 was expressed significantly in children's B-ALL and associated with poor prognostic features including poor response and treatment outcomes and could be a possible poor prognostic factor in pediatric B-cell ALL.