Swift heavy ion irradiation is an effective technique to induce changes in the microstructure and electronic energy levels of materials leading to significant modification of properties. Here we report enhancement of ammonia (NH3) sensitivity of SnO2 thin films subjected to high-energy Ni+ ion irradiation. Sol-gel-derived SnO2 thin films (100nm thickness) were exposed to 75MeV Ni+ ion irradiation, and the gas response characteristics of irradiated films were studied as a function of ion fluence. The irradiated films showed p -type conductivity with a much higher response to NH3 compared to other gases such as ethanol. The observed enhancement of NH3 sensitivity is discussed in context of ion beam generated electronic states in the SnO2 thin films.