Gene manipulation in non-adhesive cells, especially lymphocytes, was difficult due to their low efficiency and high toxicity. Electroporation was reported as a highly efficient method for human and mouse lymphocytes. However, this method requires expensive equipment and causes severe cell damage. Here, the authors present a simple and efficient method to deliver siRNA into lymphocytes with high efficiency and cell viability. This nanomaterials-based transfection reagent was simple and cost-effective and can perform multiple transfections, which further increase the overall efficiency. This method should be applicable for many cell lines and can be used to decipher gene functions of lymphocytes.