Vertically aligned MgO nanowires were epitaxially grown at 600 °C on Au-coated MgO (001) substrates by metal organic chemical vapor deposition using Mg(tmhd)2 precursor. Discrete Au particles were embedded in the wires and distributed along the central axis. Scanning and transmission electron microscopy show that the orientation, diameter, and length of the wires strongly depend on the processing conditions such as oxygen partial pressure and reactive species flow rate as well as the starting Au thickness. Diameters down to 15–20 nm were obtained. The growth can be switched from vertical to horizontal wires by decreasing the period at which reactants are supplied.