Direct printing of three-dimensional nanoscale metallic wires with controlled microstructure is useful for applications in the 3D integrated circuits, flexible electronics and nanoelectronics. In this paper, we demonstrate the localized pulsed electrodeposition process for direct printing of 3D freestanding nanotwinned Copper (nt-Cu) nanowires. Nt-Cu offers unique mechanical and electrical properties, which are advantageous in different applications. Focused ion beam (FIB) analysis confirmed the nanocrystalline nanotwinned (nc-nt) microstructure of the wires. Mechanical properties of the 3D printed nc-nt Cu were characterized using in situ SEM microcompression experiments. The 3D printed nc-nt Cu exhibited a flow stress of over 960 MPa, which is outstanding for an additively manufactured material.