We report a new strategy to fabricate a highly stable transparent heater using a Ni/Ag hybrid microgrid electrode. The microgrid-based transparent heater has a uniform heat distribution due to its electrical uniformity on an entire surface. The proposed Ni/Ag hybrid transparent heater shows outstanding optoelectronic performance (sheet resistance of 4.3 Ω /sq at transmittance of 96%). This is because the microgrid electrode not only occupies only 4% of the entire area but also has no electrical junction which may have a significant resistance. In addition, the transparent heater presents fast heating rate even at a low DC voltage by using silver (Ag) which has high thermal conductivity. Thus, our Ni/Ag hybrid transparent heater leads to high saturation temperature (up to 120 ^oC) at low DC voltage (5 V) compared to conventional transparent heater (ITO: 60 ^oC at 5 V). Furthermore, nickel (Ni) layer, a corrosion-resistant material, is coated on the Ag microgrid electrode via electroplating to improve a thermal/chemical stability. As a consequence, the proposed transparent heater exhibits no degradation of sheet resistance even under harsh environments such as a high temperature of 300 ^oC and sulfur atmosphere, confirming a effective passivation effect against thermal oxidation and sulfurization. Therefore, the use of our designed Ni/Ag microgrid electrode presents a unique opportunity to develop a high-performance transparent heater with superior long-term stability as well as a high saturation temperature at low input voltages.