Single-walled carbon nanotubes coated with crystalline tin oxide by a simple chemical-solution route are reported. The room-temperature chemical treatment results in a nominally complete and uniform coating over the entire outer surface of singular nanotubes, nanotube bundles, and also fullerene-like nanoparticles. The samples have been characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectrometry, and X-ray diffraction. The coating is composed of interconnected SnO2 nanoparticles of sizes between 1−6 nm. Typically, the coatings have a total thickness on the order of the constituent nanoparticle size.