This study aims to establish the effects of MnO doping in comparison on the yarosite mineral properties to determine its performance in the gas sensor applications. LaFeO3 doped MnO was synthesized using coprecipitation method to be applied as ethanol gas sensors. The gas sensors were fabricated into thick ceramic film using screen printing techniques and analyzed using several characterizations such as XRD, SEM and electrical properties. The XRD data showed that the materials had a cubic structure and confirmed that the crystallite size had decreased from 49.83 nm to 43.20 nm. The SEM data showed that the materials had a grained morphology with the grain size of 0.61 μm and 0.36 μm, respectively. The electrical properties showed that the materials used had a sensitivity to ethanol gases; this was established from the resistances that appeared. It could be concluded that MnO doping caused the operating temperature of LaFeO3 to become lower, decreasing from 272 °C to 268 °C. It was proven that the MnO (0.17 wt%) doping positively contributed to making the gas sensor’s properties better. Thus, the yarosite mineral that contains 0.17 wt% of MnO as impurities can be applied as the main material in gas sensor studies.