In addition to conventional wet-chemical methods for producing Sn-doped indium oxide (ITO) nanostructures, structural transformation from an ionic compound of indium hydroxide (In(OH)₃) into indium oxide (In₂O₃) is a facile route for tailoring the dimensions, morphologies and compositions of In₂O₃ nanostructures. As a novel wet-chemical approach for the synthesis of In(OH)₃ nanostructures, here we report a plasma-assisted electrolytic process where the In³⁺ and Sn⁴⁺ generated by plasma discharges on the surface of an In/Sn alloy anode hydroxylate, nucleate and grow to form single crystal In(OH)₃ nanocubes. It was found that the In(OH)₃ nanocubes reconstructively decomposed into small crystallites of bixbyite-type c-In₂O₃ with a diameter of ∼5–10 nm during the thermal transformation while the parent cube-shaped morphology of the In(OH)₃ nanocubes remained unchanged. Compositional analysis revealed that the content of Sn in the final ITO nanocube product could be effectively controlled by the starting In/Sn ratio of the alloy anode. As a result, the doping-level of Sn significantly influenced the electrical conductivity of the ITO nanocubes with the optimal conductivity of 10.47 S cm⁻¹ with a 15 wt% Sn content. The liquid-phase plasma technique is cost-effective and a continual process, and a high yield of 3.6 g hour⁻¹ could be achieved in our simple lab-scale synthetic setup, suggesting great potential for industrial mass-production of high-quality ITO nanoparticles.