Objectives: Aberrant antigenic expression in acute leukaemia is an expression of antigens which is not normally associated with acute leukaemia of that specific lineage and does not fulfil the criteria for diagnosis of Mixed phenotype acute leukaemia (MPAL). This aberrant immunophenotype can be used for the assessment of measurable residual disease (MRD) and sometimes may predict certain genetic events. Material and Methods: This was a cross-sectional study conducted in a tertiary care centre in Southern India over two years to assess the type and frequency of aberrant antigen expression in acute leukaemia by multiparameter flow cytometry. All routine cases of acute leukaemia confirmed by flow cytometric immunophenotyping were enrolled. Results: Among 244 acute leukemia cases, 84 (34%) B-ALL, 28 (11%) T-ALL, 124 (51%) AML and 8 (3%) MPAL were found. Aberrant antigenic expression was seen in 17 (20%) B-ALL, 5 (18%) T-ALL, 33 (27%) AML and 1(12.5%) MPAL. Most common aberrancy in AML was CD7(70.3%) followed by CD19 (13.5%) and CD79a (10.8%), in B-ALL was CD33(52.6%) followed by CD13 (10.5%) and CRLF2 (10.5%) and in T-ALL were CD33 and CD 79a (40% each). Conclusion: B-ALL showed a greater heterogeneity in aberrant antigens compared to AML and T-ALL. The future implication of this study is that aberrant markers can help in monitoring measurable residual disease Some aberrant phenotypes may indicate the presence of a genetic event or may be of prognostic significance. Some aberrant antigens may also be used as therapeutic targets.