Nanopowders of vanadium-tin oxides were prepared by a co-precipitation process and characterized for their bulk structures, chemical state, sensing capability, and surface reactivity. The solid solutions (cassiterite) were evaluated as sensing elements in a carbon monoxide gas sensor and as catalysts for methanol oxidation in a fixed-bed reactor. Sensing and catalytic properties were observed dependent upon doping concentration and oxidation state of vanadia species. The sensor response was favored for lower vanadium loadings (V/Sn = 0.05-0.1), related to the reduced vanadium sites. The catalytic activity for methanol conversion was favored for higher vanadium loadings (V/Sn = 0.15-0.2), related to the oxidized vanadium sites. Results demonstrate that the VOSn structure provides redox activity to facilitate oxygen activation for CO gas-sensing response and promote methanol partial oxidation to formaldehyde. Mechanistic aspects that elucidate the redox pathways are discussed. These oxide nanostructures are promising ceramic materials for use in sensing and catalysis fields involving electron transfer.