MgO mesoporous nanofibers were obtained by a template-free electrospinning method. The unique bumpy structure was obtained on the surface of nanofibers that could enhance the surface area and provide more active sites for adsorption. The formation mechanism of the bumpy-structure has been investigated. The as-prepared MgO nanofibers with a high surface area of 194.17 m(2) g(-1) exhibited excellent adsorption capacities for fluoride of 237.49 mg g(-1). Furthermore, the MgO nanofibers showed selective adsorption for different organic dyes and have superior adsorption capacity for Congo red (4802.27 mg g(-1)). The adsorption processes for both fluoride and Congo red were systematically investigated, which were found to follow the pseudo-second-order kinetic model. By comparison with the reported fabrication routes and adsorption capacities of mesoporous MgO, the synthesis process is simple, controllable and template-free, and the superior adsorption performance provided a potential adsorbent for the removal of fluoride and Congo red in wastewater treatment. The high surface area of the MgO mesoporous nanofibers might also promote its application in basic catalysis and other fields.