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+, and CD8+ T cells. Results: Significant accumulations of CD146+CD4+ cells, CD146+CD8+ cells, CD4+, CD8+, and lymphocytes in patients were compared to controls, the mean percentages of CD146+CD4+ cells, CD146+CD8+ cells, and CD146+ 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 ± 1.633 (95%CI = 18.799-25.201), while for those without complete response, it was 13 ± 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.