We report a comprehensive evaluation of the microstructures, magnetic, and hyperfine traits of Ca2+/Mg2+ co-substituted strontium nanohexaferrites (SHFs) of chemical compositions Sr1-2xCaxMgxFe12O19 (x <= 0.1). These SHFs were prepared using sol-gel unified auto-combustion strategy and characterized by diverse analytical measurements to determine the effects of Ca2+/Mg2+ co-substitution on the aforesaid properties. XRD and high resolution transmission electron microscpe (HRTEM) analyses confirmed the nucleation of HF nanocrystallites. UV-visible diffuse reflectance (DR-UV-Vis) spectra were used to evaluate the optical band gap of the proposed SHFs, which was reduced with the increase in co-substitution contents. The Fe-57 Mossbauer spectra was exploited to assess the quadrupole splitting, spectral line-width variation, isomer shift, distribution of cations (Ca2+ and Mg2+), and hyperfine magnetic fields. Measured magnetic parameters such as saturation magnetization, remanence, squareness ratio (SQR), coercivity, and magnetic moment were significantly improved due to the Ca2+/Mg2+ co-substitution. All the prepared SHFs revealed ferrimagnetic nature both at 10 and 300 K. Achieved SQR values approximate to 0.5 of the studied SHFs clearly disclosed their single domain character possessing uniaxial anisotropy.