FOXP3 has been identified as a key regulator of immune homeostasis. Mutations within the FOXP3 gene result in dysregulated CD4⁺ T‐cell function and elevated cytokine production, leading to lymphoproliferative disease. FOXP3 expression in CD4⁺ T cells is primarily detected with the CD4⁺ CD25⁺ regulatory T‐cell population. In humans the protein is detected as a doublet following immunoblot analysis. The lower band of the doublet has been identified as a splice isoform lacking a region corresponding to exon 2. The aim of this study was to investigate whether the splice variant form lacking exon 2 and a new novel splice variant lacking both exons 2 and 7, were functional inhibitors of CD4⁺ T‐cell activation. The data generated showed that full‐length FOXP3 and both splice variant forms of the protein were functional repressors of CD4⁺ T‐cell activation.