The structural and optical properties, as well as dielectric characteristics at various frequencies (0.1 Hz—20 MHz) and temperatures, T (300–400 K), of hydrothermally synthesized SnO₂ nanoparticles, Cu/SnO₂, and Fe/SnO₂ composites have been investigated. The crystal structure is mostly formed of a tetragonal SnO₂ phase, with a second phase of monoclinic CuO or rhombohedral Fe₂O₃ detected in Cu/SnO₂, and Fe/SnO₂ composites, respectively. The direct optical band gap, residual dielectric constant, and density of charge carriers are increased, while ac conductivity (σ_ac) and dielectric constant decreased in Cu/SnO₂ and Fe/SnO₂. The value of σ_ac was decreased while the electric Q-factor was increased by increasing T. SnO₂ obeyed the hole-conduction mechanism for 400 ≥ T (K) ≥ 300, while Cu/SnO₂ and Fe/SnO₂ obeyed the electronic-conduction mechanism for 400 ≥ T (K) > 300. The binding energy is independent of T for SnO₂, whereas it increases with rising T for Cu/SnO₂ and Fe/SnO₂ composites. F-factor and electronic polarizability are improved by a rise of T for SnO₂ and Cu/SnO₂ meanwhile are decreased for Fe/SnO₂. The electrical impedance of the grains and their boundaries as well as equivalent capacitance are increased by increasing T and have higher values for Fe/SnO₂ at T > 300 K. The obtained results recommend the synthesized Cu/SnO₂ and Fe/SnO₂ composites to be used as catalysts for water purification, anodes for lithium batteries, supercapacitors, and solar cell applications amongst others.