Mesoporous LaFeO₃with high surface area and pore volume was prepared through a nanocasting route by using mesoporous silica SBA-15 as a hard template. The structure and chemical composition of the sample were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS). The humidity sensing properties of the mesoporous LaFeO3 were investigated. Impedance greatly changes by more than five orders magnitude (1.7 × 106 to 4.5 kΩ) when the relative humidity varies from 11% to 98% at 10 Hz, and it also exhibits the satisfactory response time, hysteresis and stability. The sensor utilizing mesoporous LaFeO₃via nanocasting method displays superior humidity performance compared to that using bulk LaFeO₃via sol–gel technique. Such sensing behavior of the mesoporous LaFeO₃can be attributed to the high surface area (83.2 m2/g) and porosity, which lead to highly effective interaction between the water molecules and the surface active sites. A possible mechanism is discussed to explain the excellent performance of the humidity sensing device using the mesoporous LaFeO₃.