A method for aptamer directed conjugation of DNA to therapeutic antibodies has been developed. In the method, an antibody selective aptamer binds to a specific site in the constant domain of human IgG1 antibodies and is used for both templated and direct conjugation to the antibodies. Through optimization of the design and reaction conditions, the antibody-DNA conjugates could be produced efficiently using equal stoichiometry of protein and DNA. Three different antibodies were evaluated, and the conjugates were characterized by anion exchange chromatography and SDS-PAGE. The conjugation sites for one of the antibodies were determined by MS/MS analysis of the digested conjugate. The antibody-DNA conjugate was also tested for receptor binding on cell surfaces showing retained binding.