In the present study, Au-V₂O₅ sensing material was tested as a sensing electrode for developing mixed-potential ammonia gas sensors. The results of gas sensing measurements indicated selective responses to NH₃ while this selectivity was highly dependent on the temperature. Different V₂O₅ contents were tested in the sensing electrode. The results showed that by increasing V₂O₅ content from 15 wt.% to 50 wt.%, selective ammonia sensors could be achieved at 550 °C. The selectivity of Au-50%V₂O₅ sensor was also confirmed in gas mixtures of CO, NH₃, NO, and NO₂ gases. Modeling of the sensor responses in the ammonia concentration range 2-40 ppm at four oxygen concentrations was performed based on mixed-potential theory. Nernst and Butler-Volmer equations with an electron transfer assumption were used for data modeling.