We have developed a novel antibody-drug conjugate (ADC) that can selectively deliver the Lck inhibitor dasatinib to human T lymphocytes. This ADC is based on a humanized antibody that selectively binds with high affinity to CXCR4, an antigen that is selectively expressed on hematopoietic cells. The resulting dasatinib-antibody conjugate suppresses T-cell-receptor (TCR)-mediated T-cell activation and cytokine expression with low nM EC50 and has minimal effects on cell viability. This ADC may lead to a new class of selective immunosuppressive drugs with improved safety and extend the ADC strategy to the targeted delivery of kinase inhibitors for indications beyond oncology.