AbstractSummary: This paper reports a study of the sorption properties of thin Ta2O5 films to NH3 vapors. The films are deposited using electron beam evaporation. In order to determine the sorption ability of Ta2O5 to NH3, a quartz crystal microbalance (QCM) with a thin Ta2O5 film is investigated. The Ta2O5 film is used as a receptor for the NH3 gas. The AT‐cut, 14 MHz quartz resonators allow conversion of the additional mass loading that occurs as a result of sorption into a frequency shift. The experiments are carried out by measuring the resonant frequency shift of the QCM to vapors from an aqueous solution of NH3 with different concentrations from 10 to 10 000 ppm. The obtained experimental results indicate that the variations of the resonant frequency are a function of the ammonia concentration and the thickness of the Ta2O5 layer. The process of sorption is found to be reversible. The reported investigation shows that a QCM covered with a thin Ta2O5 layer is sensitive to ammonia vapors at room temperature and is able to detect NH3 concentrations in the investigated range (10–10 000 ppm).Relative change of QCM frequency versus ammonia concentrationimageRelative change of QCM frequency versus ammonia concentration