The delivery of bispecific antibodies (BsAbs) targeting B-cell maturation antigen (BCMA) and CD3 using the gene therapy approach is a promising alternative for BsAb administration in patients with multiple myeloma (MM). In the present study, we evaluated the efficacy of this approach using a xenograft model. Tumour growth was significantly delayed in mice treated with single electroporation-enhanced intramuscular injection of plasmid DNA encoding BCMA/CD3 BsAb in contrast to the vehicle control-treated group. Limited toxicity was observed following treatment. This study demonstrates that the gene therapy-based approach for the delivery of BCMA/CD3 BsAb is effective and safe for the treatment of MM.