We report a comprehensive study of dc and ac conductivity, dielectric relaxation and capacitance voltage characteristics of Mn doped ZnO nanocrystalline semiconductors prepared by mechanical alloying. Samples are characterized by HRTEM and XRD. Direct current conductivity increases with the increase in temperature and the thermal behavior of electrical dc conductivity for the investigated samples can be described by adiabatic polaronic hopping model. The frequency dependent conductivity obeys a power law sigma' (f) proportional to f(s)T(n). The temperature exponent n strongly depends on frequency. Analysis of the temperature dependence of frequency exponent s suggests a transformation from large polaron to small polaron conduction model with increase in temperature. Considering electric modulus the dielectric properties of the samples have been explained. Capacitance-voltage characteristic suggests the formation of Schottky diode between metallic electrode and semiconductor junction and diode parameter shows anomalous behavior with increasing milling time. (C) 2016 Elsevier Ltd. All rights reserved.