The competitive adsorption of phosphate and nitrate from aqueous solution on calcined Mg-Al layered double hydroxides (Mg-Al CLDHs) were investigated. Experiments were carried out as a function of adsorbent dosage, contact time, initial pH and temperature. The adsorption processes of phosphate and nitrate were followed by the pseudo second-order and pseudo first-order kinetics, respectively. The X-ray diffraction patterns (XRD) showed structural reconstruction during sorption, the unchanged d-spacing d₀₀₃ indicated phosphate and nitrate were mainly adsorbed on the surface and the near-edge interlayer. The results of Fourier transformed infrared spectroscopy (FTIR) verified nitrate and phosphate adsorbed onto the CLDHs. Desorption behaviors indicated that nitrate can be more easily desorbed from loaded CLDHs than phosphate. The possible mechanism of phosphate adsorption was controlled by chemisorption, while nitrate adsorption was governed by physisorption. The results showed that the Mg-Al CLDHs can be used to simultaneously remove phosphate and nitrate from aqueous solution.