Flowerlike alpha-Fe2O3 nanostructures were synthesized via a template-free microwave-assisted solvothermal method. All chemicals used were low-cost compounds and environmentally benign. These flowerlike alpha-Fe2O3 nanostructures had high surface area and abundant hydroxyl on their surface. When tested as an adsorbent for arsenic and chromium removal, the flowerlike alpha-Fe2O3 nanostructures showed excellent adsorption properties. The adsorption mechanism for As-V and Cr-VI onto flowerlike alpha-Fe2O3 nanostructures was elucidated by X-ray photoelectron spectroscopy and synchrotron-based X-ray absorption near edge structure analysis. The results suggested that ion exchange between surface hydroxyl groups and As-V or Cr-VI species was accounted for by the adsorption. With maximum capacities of 51 and 30 mg g(-1) for As-V and Cr-VI, respectively, these low-cost flowerlike alpha-Fe2O3 nanostructures are an attractive adsorbent for the removal of As-V and Cr-VI from water.