Tetracycline (TC) is one of the antibiotics, which is detected at high titre in aquatic systems, inducing microbial resistance. This study highlights the adsorptive removal of TC by activated carbon (AC) using low temperature carbonization obtained from Ulva prolifera macroalgal biomass – an abundantly available algae in southern Indian beaches. The AC had rough, irregular, and porous structure with large specific surface area of 197.53 m2/g. The adsorption data was modelled using adaptive neuro-fuzzy inference system that fitted the data satisfactorily. Pseudo-second-order kinetics well-suited TC adsorption confirming to chemisorption. Both Langmuir and Freundlich isotherms suited-well to the data with monolayer adsorption capacity of 54.04 mg/g, which emphasized the suitability of using the algal biomass-derived AC for TC removal over other adsorbents. Therefore, the present investigation highlights the use of a new low-cost nanoadsorbent developed from algal biomass along with the tremendous potential of ANFIS in predicting the adsorption process. Display omitted •Activated carbon was synthesized using Ulva prolifera macroalgal biomass by low temperature carbonization.•Tetracycline adsorption followed both Langmuir and Freundlich isotherms.•The adsorption data was modelled using adaptive neuro-fuzzy inference system (ANFIS).•The monolayer adsorption capacity was 54.04 mg/g.