New negative temperature coefficient (NTC) ceramics based on CaCu3-xMnxTi4O12 (0 <= x <= 1) compositions have been investigated. The grain size of the CaCu3-xMnxTi4O12 samples decreases at first and then increases with increasing Mn content. The X-ray photoelectron spectroscopy analysis corroborates the presence of Mn3+ and Mn4+ in Mn-doped samples, which results in a decrease in the activation energy. All the NTC thermistors prepared show a linear relationship between the natural logarithm of the resistivity and the reciprocal temperature, indicative of NTC characteristics. The Mn-doped CaCu3-xMnxTi4O12 NTC thermistors provide various electrical properties, depending on Mn content. The values of p25, B constant and activation energy of the NTC thermistors are in the range of 2.22 x 10(6)-3.22 x 10(-8) Omega cm, 5488-8031 K, and 0.473-0.692 eV, respectively.