Ce and Y substituted SrFe12O19 (x = 0.4 and 0.5) nanohexaferrites have been synthesised by sol–gel auto-combustion. The pure hexagonal SrFe12O19 phase was confirmed by XRD, FE-SEM and HR-TEM. The ac conductivity and dielectric properties of Ce and Y substituted Sr:Fe12O19 nanohexaferrites were studied by using complex impedance technique. Dielectric properties such as dielectric constant, dielectric loss, dielectric tangent loss, as well as ac conductivity are measured at various bias potentials in a varying frequency range from 10 Hz to 10 MHz. The frequency dependency of the ac conductivity could be evaluated by a power exponent law at higher frequencies, which is a characteristic mechanism for electrical charge transport by tunnelling processes with which it is more dispersive at lower frequencies. The conduction mechanisms were also investigated at various dc bias potentials, mainly being an indicative of hopping type conduction. So, the dielectric dispersion behaviour can be well elucidated in terms of Maxwell–Wagner polarization in accordance with the Koop’s phenomenological theory. Utilizing an electrical equivalent circuit model, impedance studies were carried out in a specific frequency domain to characterize all the contributions of the dielectric response between the grains and grain boundaries to the dielectric parameters.