The biochars derived from alfalfa (AF) and bermudagrass (BG), the abundant grass hays to cows, were prepared, characterized and used for removal of tetracycline (TC) in water. The alfalfa-derived biochar (AF-BC) has exhibited outstanding TC adsorption capacity (372 mg/g), which was about 8-fold higher than that of bermudagrass-derived biochar (BG-BC). In addition, the TC adsorption capacity of AF-BC was comparable with those of the commercial activated carbons under the same conditions. The surface structure, chemistry and high ash contents of AF-BC suggested the hydrogen bonding, electrostatic interactions and surface complexation between AF-BC and TC. Furthermore, hydroxyapatite (HAP; Ca-5(PO4)(3)OH) and calcite (CaCO3) on the surface of AF-BC may also contribute to adsorption of TC via surface complexation, hydrogen bonding and electrostatic interactions. The alkaline desorption-driven regeneration of TC-spent AF-BC led to effective adsorption-desorption for multiple cycles, which indicated AF-BC could be a cost-effective adsorbent for TC in water and wastewater.