Here, NiMn₂O₄ and NiZn_0.2Mn_1.8O₄ nanocrystalline ceramic powders are fabricated, characterized, and compared for thermistor applications. Solution route was used to synthesize the materials. The NiMn₂O₄ is a spinel single crystal material with the average crystallite size 26.82 nm and a particle size less than 1 μm and has uniform morphology. The EDS results confirmed the composition of NiMn₂O₄ that consisted of Ni, Mn, and O₂ only. The average crystallite size of NiZn_0.2Mn_1.8O₄ is 37.48 nm and the particle size is less than 0.5 μm. There has been observed some agglomeration formation due to high calcination temperature. The β-value of NiMn₂O₄ is larger than NiZn_0.2Mn_1.8O₄, hence thermistors constructed from NiMn₂O₄ are more stable and applicable as NTCR thermistor powder.