The center of this work is to interpret the role of particle sizes of starting oxides on the properties of spinel-type Mn1.1Co1.5Fe0.4O4 negative temperature coefficient ceramics. Investigations were conducted using the traditional solid-state reaction route. The optimized microstructure of Mn1.1Co1.5Fe0.4O4 ceramics was achieved by utilizing the appropriate proportion of micron- and nano-sized particles. Distortion of the [MnO6] octahedron and the effects of grain sizes generate significant changes in resistivity while without inducing many changes in the B-25/50 value (3700 K). Aging analysis indicates that the use of nano-sized particles deteriorates the stability of Mn1.1Co1.5Fe0.4O4 ceramics, i.e., the Delta R/R-0 hugely increases from 0.5% to 15.1% after accelerated aging at 200 degrees C for 800 h. This work will provide clear guidance for the selection of raw materials from the actual research to the production process.