Flow cytometry is an important technique for characterization of immune cells, with accurate lymphocyte profiling being essential for clinical diagnostics and research applications. While immediate processing of blood samples is ideal, long-term storage solutions are needed for large-scale studies or settings without immediate access to laboratory facilities. TransFix® is a chemical stabilization solution that allows delayed analysis by preserving cell morphology and surface markers. However, the impact of long-term cryopreservation in TransFix® on lymphocyte integrity remains underexplored. In this study, we evaluated the efficacy of cryopreservation in TransFix® for maintaining the proportions of key lymphocyte subsets, including CD3⁺ T cells, CD3⁺CD4⁺ T helper cells, CD3⁺CD8⁺ cytotoxic T cells, CD19⁺ B cells, and CD16⁺/CD56⁺ natural killer cells. Blood samples were cryopreserved in TransFix® for varying time periods, up to 48 months, and compared to fresh samples using flow cytometry. The results show that the proportions of lymphocyte subsets remain stable during cryopreservation for up to 48 months, with no significant differences observed between fresh and cryopreserved samples. This suggests that TransFix® can successfully preserve lymphocyte integrity for long-term storage, providing a reliable option for delayed analysis. These results highlight the usefulness of TransFix® for studies that require extended storage, making it easier to conduct immune monitoring in a wide range of settings.