In this study, polyethylene 2,6-naphthalate (PEN) was selected as a substrate to fabricate a flexible conducting electrode through the solution process. The sandwiched silver nanowire (AgNW) electrode between the poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) layers fabricated on the flexible PEN substrate was successfully prepared, which exhibited a moderately high electrical conductivity and surface smoothness suitable for polymer solar cells. Notably, the sheet resistance of the PEDOT:PSS/AgNW/PEDOT:PSS film was 22Ω/□, and it exhibited the transmittance of 82% at the wavelength of 550 nm, although PEN was used as the substrate. This electrode film can be easily employed as an anode, and when it is applied as an electrode in a polymer solar cell, it reveals a comparable performance to that of indium tin oxide-based devices. This simple and effective fabrication of flexible conductive electrodes is envisaged to contribute immensely to future research on flexible electronics and optoelectronics.