A negative temperature coefficient (NTC) thermistors based on BaFe (x) Sn1-x O3-epsilon were fabricated by conventional solid-state reaction method. The microstructure and electrical properties of the NTC thermistors were characterized by X-ray diffraction (XRD), electric (R(T)), and impedance measurements. The XRD analysis shows that the BaFe (x) Sn1-x O3-epsilon still remains cubic perovskite structure and the crystal growth orientation changes at higher Fe content. Similarly, the electric measurements indicates that all the samples show typical NTCR behavior; with increasing Fe content, the room temperature resistivity, activation energy, and thermistor constant decrease, are in the range of 2.52-217 K Omega cm, 0.343-0.43 eV, and 3900-4896 K, respectively. The impedance spectroscopy confirms that the observed ac resistance, consisting of the grain bulks, grain boundaries, and electrode-ceramic interface, mainly attributes to the grain boundaries and grain bulks; with the rise in temperature the grain boundary resistance shows more rapid change than the grain resistance; moreover, the Fe concentration can greatly affect the grain and grain boundary resistance.