Grain core and grain boundary electrical and dielectric properties of nanocrystalline yttria-stabilized zirconia (YSZ) were analyzed using a novel nano-Grain Composite Model (n-GCM). Partially sintered pellets with average grain sizes ranging from 10 to 73 nm were analyzed over a range of temperatures using AC impedance spectroscopy (AC-IS). Local grain core and grain boundary conductivities, grain boundary dielectric constants, and effective grain boundary space charge widths were determined from the fitted circuit parameters. Required grain core dielectric constant data were provided by AC-IS measurements of single crystal YSZ over a range of temperatures. The local grain core conductivity of all the nanocrystalline samples was slightly decreased with respect to that of microcrystalline YSZ. Conversely, the local grain boundary conductivity was enhanced up to an order of magnitude compared to microcrystalline YSZ. At the nanoscale, there was a noticeable increase in local grain boundary dielectric constant versus single crystal values at the same temperature.