The removal of antibiotics by adsorption was considered to be a cheap and efficient treatment method. Herein, magnetic NiFe₂O₄/biochar (NFO/BC) composites were prepared by hydrothermal growth of nickel ferrite nanoparticles on sawdust derived biochar. It was found that NFO/BC composites had developed pore structure, rich oxygen-containing functional groups, and strong magnetism. The maximum adsorption capacity of the prepared magnetic composite for tetracycline (TC) was 420.41 mg g⁻¹. The results of adsorption thermodynamics and adsorption kinetics showed that the adsorption process is a spontaneous process, which conforms to Langmuir model and pseudo second-order kinetic model. The influence experiment of pH and ionic strength confirmed that electrostatic interaction and hydrogen bonding are the key factors affecting the adsorption process. Additionally, pore filling and π-π interaction also existed in the adsorption process of tetracycline. This recyclable magnetic composite provides a feasible research idea for the efficient removal of antibiotics from water. Graphical Abstract