New negative temperature coefficient (NTC) ceramics based on xMgAl 2O4-(1 - x)LaCr0.5Mn0.5O3 (x = 0, 0.4, 0.6, 0.8) composition were investigated. The composite ceramics (x = 0.4, 0.6, 0.8) consisted of two phases: a cubic spinel MgAl2O 4 phase and an orthorhombic perovskite LaCr0.5Mn 0.5O3 phase isomorphic to LaCrO3. The brighter regions were the LaCr0.5Mn0.5O3 and the darker was the MgAl2O4. There was ion diffusion between these two phases. X-ray photoelectron spectroscopy analysis corroborated the presence of Cr3+, Cr4+, Mn3+ and Mn4+ ions on lattice sites, which may result in the hopping conduction. The ρ 300 and B 400/800 constant increased with increasing MgAl2O4 content. The values of ρ 300, B 400/800 and activation energy of NTC thermistors were in the range 1.76-1.22 × 108 Ωcm, 2,646-8,711 K, 0.228-0.746 eV, respectively. This means the electrical properties can be adjusted to desired values, depending on the MgAl2O4 content.