The present invention relates to a multi-specific antibody conjugate (such as, a bispecific antibody conjugate), and a related composition, therapeutic method and use thereof. The antibody conjugate comprises a multispecific antibody, such as a bispecific antibody, conjugated to a nanomaterial. The antibody conjugate can be used to modulate an immune response, treat or prevent a disease or condition (e.g., a cancer, autoimmune disease, pathogen infection or inflammatory disease), etc.