Uniform conjugates combining a DNA aptamer (either anti-MUC1 or ATP aptamer) and a synthetic polymer segment were synthesized by automated phosphoramidite chemistry. This multistep growth polymer chemistry enables the use of both natural (i.e., nucleoside phosphoramidites) and non-natural monomers (e.g., alkyl- and oligo(ethylene glycol)-phosphoramidites). Thus, in the present work, six different aptamer-polymer conjugates were synthesized and characterized by ion-exchange HPLC, circular dichroism spectroscopy, and electrospray mass spectrometry. All these methods evidenced the formation of uniform molecules with precisely controlled chain-length and monomer sequences. Furthermore, aptamer folding was not affected by polymer bioconjugation. The method described herein is straightforward and allows covalent attachment of homopolymers and copolymers to biofunctional DNA aptamers.