In this work, M‐type strontium nanohexaferrites with chemical composition Ba0.8−xSr0.2LaxFe12−x−yNixZnyO19 (x = 0.00, 0.05, 0.10; y = 0.00, 0.08, 0.16) are prepared using sol–gel auto‐combustion technique. The formation of single phase hexagonal ferrites is confirmed from XRD analysis. It also reveals the presence of magnetite and the crystallites sizes are in the range of 21.31–29.91nm. The lattice constants are found to decrease with an increase in cation substitution. The FTIR spectra of the sample show three dominant peaks in the range of 400–600 cm–1 which indicate the formation of the desired hexaferrite structure. The field emission scanning electron microscope images reveal large crystallites with shapes close to the hexagonal platelet‐like whose sizes are nonuniformly distributed. Also, agglomeration is observed due to magnetic interactions between the crystallites. The dielectric constant, dielectric loss, conductivity, and dielectric modulus are analyzed using the Maxwell–Wagner model. Dielectric constant is enhanced at high frequency in the entire sample and reduction of dielectric loss is also observed with further cations substitutions.