<p>Physicians rely on reference values from healthy populations to guide clinical decisions regarding B-cell subpopulations in primary immunodeficiency. While age-dependent reference ranges have been reported in several populations, no study has established these values for Malaysian children. Given that B-cell subpopulation distributions may vary between populations, we aimed to define reference ranges for total B cells, transitional B cells, naïve B cells, total memory B cells, switched and non-switched memory B cells, and plasmablasts in Malaysian children aged 2 to 15 years. Blood samples taken from 85 children aged 2 to 15 years were evaluated for the distribution of B cell subsets. Absolute numbers and percentages were determined for total B cells (CD19⁺), transitional B cells (CD19⁺CD27⁻CD24^+ brightCD38^+bright), naïve B cells (CD19⁺CD27⁻IgD⁺), total memory B cells (CD19⁺CD27⁺), class-switched memory B cells (CD19⁺CD27⁺IgM⁻IgD⁻), non-classical switched memory B cells(CD19⁺CD27⁻IgM⁻IgD⁻), non-switched memory B cells (CD19⁺CD27⁺IgM⁺IgD⁺), and plasmablasts (CD19⁺CD27⁺CD38^+ bright). We observed age-dependent variations in most B-cell subpopulations, with naïve B cells being predominant, followed by memory B cells, while plasmablasts were present in trace amounts across all ages. Additionally, certain of B-cell subpopulations (total memory B cells and class-switched memory B cells) were observed at higher frequencies in female children compared to males. This study provides age-specific reference values for B cell subsets in a paediatric population, which may serve as a valuable guideline for diagnosing children with suspected immunodeficiency.</p>