This study provides an insight to understanding the role of thickness on the hopping frequency (v(0)) of electrons between Mn3+ and Mn4+, the temperature coefficient of resistance (alpha(T)) and the characteristic temperature (T-0) in Mn-Co-Ni-O spinel films. A remarkable decrease in the Mn3+/Mn4+ ratio of films from 265 to 693 nm and an increase in the range of 693-887 nm can be probed by x-ray photoelectron spectroscopy. From the analysis of the Hall measurements, it is found that both the 1/v(0) and alpha(T) = 303K increase with the thickness below 693 nm, and then decrease above 693 nm. Such a feature is attributed to the change in the distribution of Mn cation. The T-0 are 3675, 3352, 3087, 3366 and 3816 K for films with thicknesses from 265 to 887 nm. It reveals that the ratio of Mn3+/Mn4+ should also be responsible for T-0, which can result in significantly different electrical properties of Mn-Co-Ni-O films with increasing thickness. The present result will open a way to design a desired negative temperature coefficient thermistor by adjusting the thickness of films.