SnO₂ nanoparticles have been prepared by a continuous flow hydrothermal method using SnCl₄∙5H₂O and aqueous sodium hydroxide as precursor solutions. The syntheses were carried out in an experimental matrix of four different precursor pH values (1, 3, 7 and 11) and four different temperatures (250, 300, 350, 400 °C). Both temperature and pH affect the crystallite size and morphology providing considerable synthesis control over the nanoparticle characteristics. At intermediate pH (3 and 7) quite spherical nanoparticles are obtained and higher synthesis temperature results in larger nanoparticles (3–6 nm). A highly peculiar behavior is observed at either low pH (1) or high pH (11), where larger anisotropic nanorods (width 6−9 nm, length 20−40 nm) are obtained for the reaction near or in the supercritical regime (350 and 400 °C). Pore size and band gap were determined for all products, and selected samples were tested as anode materials in Li ion batteries.