Monodisperse, water-soluble dextran-coated iron oxide (Fe(3)O(4)) nanorods were synthesized using a facile and scalable approach. Our room temperature method involves the mixing of an acidic solution of iron salts with a basic solution of ammonium hydroxide to facilitate initial formation of iron oxide crystals. The stability, crystalinity and shape of these nanorods depends on the time of addition of the dextran, as well as the degree of purity of the polymer. The as-synthesized nanorods exhibit unique magnetic properties, including superparamagnetic behavior and high spin-spin water relaxivity (R2). Additionally, they possess enhanced peroxidase activity when compared to those reported in the literature for spherical iron oxide nanoparticles. Thus, this high yield synthetic method for polymer-coated iron oxide nanorods will expedite their use in applications from magnetic sensors, devices and nanocomposites with magnetic and catalytic properties.