The structural parameters, optical properties, and dielectric constants at a frequency (f) range of 0.1–20 MHz, and temperature (T) range of 300–400 K of hydrothermally synthesized M/SnO₂ nanocomposites (for simplicity M denotes oxides of Al, Ni, or Mn) were compared. Rietveld refined X-ray powder diffraction (XRD) analysis demonstrated the formation of hexagonal, cubic, or spinel crystal structures of Al₂O₃, NiO, or Mn₃O₄ phases, respectively, besides the tetragonal rutile crystal structure of SnO₂. The impact of Al addition on the optical band gap of SnO₂ is negligible while it decreased or increased by incorporation of Ni or Mn, respectively. The residual lattice dielectric constant of SnO₂ was increased, while the real part of the dielectric constant and the ac conductivity of SnO₂ were decreased by M incorporation. The dielectric parameters are remarkably affected by selected M, T, and f values and their changes agree with the Maxwell-Wagner model. The Q-factor of SnO₂ was increased by M addition while decreased with increasing T. The Ni/SnO₂ obeys the hole conduction at T ≤ 330 K, while Mn/SnO₂ and Ni/SnO₂ obey the electronic conduction at T > 330 K. The binding energy is independent of the chosen T for SnO₂, whereas it sharply increases for Ni/SnO₂ and slightly decreases for Al/SnO₂ and Mn/SnO₂. The F-factor of SnO₂ was slightly decreased by M addition, but it was increased with T for SnO₂, Al/SnO₂, and Mn/SnO₂ while was decreased for Ni/SnO₂. The Cole-Cole plots for M/SnO₂ composites were analyzed, and the components of the equivalent circuit were determined. The electrical impedance, resistance of grains, resistance of grain boundaries, and equivalent resistance of SnO₂ were increased by M incorporation, whereas equivalent capacitance was decreased. The findings recommend the SnO₂-based nanocomposites for applications in optoelectronics, lithium batteries, supercapacitors, and solar cell devices.