Highly ordered sisal-like cobalt superstructures with novel turreted branches were prepared by a simple hydrothermal reduction route. The synthetic process involved the chemical reduction of cobalt ions and the oriented growth of cobalt nanocrystals under kinetic control independent of surfactants or external magnetic fields. The as-obtained products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and vibrating sample magnetometer (VSM). The sisal-like superstructures were found to be assembled by well-aligned turreted cobalt branches radiating from the center. The size and morphology of the products could be tailored by properly tuning the process conditions and the component of the reaction solution. The magnetic properties of the products were studied as well and the results demonstrate that the products presented ferromagnetic properties related to the corresponding microstructures. Based on a series of contrast experiments, the probable growth mechanism and fabrication process of the products were proposed. This work provides a simple and effective strategy to fabricate self-assembled cobalt hierarchical structures with novel and tunable morphologies. (C) 2010 Elsevier B.V. All rights reserved.