The most crucial blood group system in transfusion medicine is still the ABO system. Any unresolved discrepancy could result in the patient receiving blood that is incompatible and could trigger acute intravascular hemolysis. ABO subgroups are one of the astounding differences in blood grouping. The amount of A and B antigens carried by red blood cells and present in secretion varies depending on the ABO subgroup phenotype. Clinically, A1 and A2 are the two most frequently observed subtypes. Many weaker A subgroups have been described, including A3, Axe, am, and el. This example involves an Indian male donor who was initially misclassified as a Group O individual before being identified as an Ax/Aweak subgroup phenotypically. The next-generation sequencing defined the genotype of this case as ABO*AW.31.01/*O.01.75.