We describe a technique to synthesize DNA homopolymers on a surface using surface-initiated enzymatic polymerization (STEP) with terminal deoxynucleotidyl transferase (TdTase), an enzyme that repetitively adds mononucleotides to the 3'-end of oligonucleotides. The thickness of the synthesized DNA layer was found to depend 14 on the deoxymononucleotide monomer, in the order of dATP > dTTP >> dGTP approximate to dCTP. In addition, the composition and the surface density of oligonucleotide initiators were also important in controlling the extent of DNA polymerization. The extension of single-stranded DNA chains by STEP was further verified by their binding to antibodies specific to oligonucleotides. TdTase-mediated SIEP can also be used to grow spatially defined three-dimensional DNA structures by soft lithography and is a new tool for bioinspired fabrication at the micro- and nanoscale.