The thermal response of a micro-thermal sensor at the slider–disk interface filled with helium–air gas mixtures is investigated. The heat transfer due to both the heat conduction in gas films and the near-field radiation is included. The effects of the helium fraction on the sensor temperature are discussed. The results show that due to the evanescent photo tunneling at a small spacing, the near-field radiation generates a large heat flux, resulting in decreases in the sensor temperature. However, at a large spacing over 10 nm, the heat transfer is dominated by the heat conduction in gas films. An increasing helium fraction causes an increase in the heat conduction and a consequent decrease in the sensor temperature.