Structural, magnetic, and optical properties along with N-2 absorption-desorption features of Sm3+-Dy3+ ions co-substituted BaSr hexaferrite microspheres (HFMSs) engineered through a hydrothermal gel approach were investigated. The microstructural and morphological features were examined by powder X-ray diffraction (XRD), surface area and pore size distribution (BET), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), and transmission electron microscopy (TEM) techniques. Rietveld analysis proved the purity of products. The BET revealed a slight variation in textural characteristics with increasing Sm3+-Dy3+ substitution. The surface area (11-16 m(2)/g) exhibits a pore volume of similar to 0.07 cm(3)/g and average pore size distributions of 26.6 nm. The 300 K and 10 K field-dependent hysteresis loops were registered. Remanent magnetizations (M-r) and coercive fields (H-C) are in a range of 29.15-34.05 emu/g and 1420-5391 Oe at 300 K, respectively. The estimated saturation magnetizations (M-s) vary between 53.22 emu/g and 71.08 emu/g, and magneton numbers (n(B)) are in a range of 10.51-13.93 mu(B). At 10 K, the M-r = 35.18-46.83 emu/g, H-C = 1487-4760 Oe, M-s = 81.82-99.17 emu/g, and n(B) = 14.83-19.44 mu(B), which are greatly higher compared to room temperature. All magnetic parameters exhibit strong ferrimagnetic features of pristine Sr0.5Ba0.5Fe12O19 and Dy3+ and Sm3+ co-doped HFMSs at both temperatures. Squareness ratios (SQRs), which are very close to 0.50 assign the single domain uniaxially symmetric structured HFMSs. delta M type of remanence plots was applied to specify the intensity and type of interparticle interactions as a function of the externally magnetic field, H. The Schuster-Kubelka-Munk theory provides to estimate direct energy band gaps (E-g). Undoped or co-doped HFMSs have a very narrow magnitude of E-g data between 1.795 and 1.865 eV depending on the couple ion concentrations.