We demonstrate a self-cleanable, waterproof, highly transparent, and flexible Ag network covered by a very thin transparent polytetrafluoroethylene (PTFE) layer using typical magnetron sputtering for multi-functional flexible thin film heaters used in smart windows. By passivation of the self-assembled Ag network with very thin PTFE films, we fabricated a multi-functional Ag network suitable for flexible thin film heaters. At a PTFE thickness of 10 nm, the Ag network passivated by hydrophobic PTFE layer showed a low sheet resistance of 11.64 Ohm/square, high optical transmittance of 80.20% at a wavelength of 550 nm, and high contact angle of 102.42°. In addition, sputtering of the PTFE layer on the Ag network improved the mechanical flexibility and reliability of the Ag network electrode. The flexible and transparent thin film heater (TTFH) with Ag network electrode covered by PTFE layer showed a saturation temperature of 120 °C at low voltage of 4.5 V and power of 2.45 W, as well as a hydrophobic surface suited for self-cleaning smart windows. These multi-functional performances of TTFH indicate that the Ag network/PTFE film-based flexible TTFH could be used as self-cleanable, waterproof TTFHs for curved smart windows in smart buildings and automobiles.