Introduction: The diagnosis of acute leukemia relies on the integration of morphological and immunophenotypic findings. Flow cytometry is of particular value in morphologically ambiguous cases or in myeloperoxidase (MPO)-negative cases. Objective: To evaluate the contribution of flow cytometric immunophenotyping to the diagnosis and classification of acute leukemias and to assess its concordance with cytological findings. Methods: A retrospective study was conducted in 62 patients with acute leukemia. Demographic, clinical, hematological, and cytological data were collected. Flow cytometric immunophenotyping was performed to determine lineage and characterize antigen expression by blast cells. Concordance between cytological and immunophenotypic classifications was assessed. Results: The study population comprised 43 men (69.35%) and 19 women (30.65%), with a median age of 62 years. Anemia and thrombocytopenia were observed in 91.94% and 88.71% of patients, respectively. Cytology identified 33 cases of acute myeloid leukemia (AML) and 21 MPO-negative acute leukemias. Immunophenotyping classified 41 cases as AML and 14 as acute lymphoblastic leukemia (ALL). Overall concordance between the two approaches was 83.87%, whereas discordance was observed in 16.13% of cases. Among AML cases, CD33 (80.49%), MPO (78.05%), CD13 (75.61%), and CD117 (75.61%) were the most frequently expressed markers. Aberrant CD7 expression was observed in 29.27% of cases. Conclusion: Flow cytometric immunophenotyping provides an important complementary diagnostic contribution, particularly in MPO-negative acute leukemias and discordant cases. Its combination with cytological examination improves lineage assignment and classification of acute leukemias.