In this work, we report a simple strategy for synthesis of graphene oxide nanostructures with various morphologies including single-, few-layer, and three-dimensional networks. Morphology control is achieved by adding different amounts of Ni2+ into a one-step hydrothermal process. The involved growth mechanisms for the morphology control are discussed. A random arrangement of graphene oxide nanosheets is suggested to induce the networks' formation. Ni2+ facilitates the formation of graphene oxide's preferential face-to-face overlapping structure, and high Ni2+ concentrations render adjacent graphene oxide sheets to combine each other tightly to form closely packed, layered structures. Compared with single-, few-layer graphene oxide, the electrode prepared by three-dimensional networks has a mass specific capacitance of 352 F g(-1) at v = 5 mV s(-1), which is much higher than that of recently reported three-dimensional graphene oxide nanostructures (240 F g(-1)).