In this study, adsorption of Remazol Brilliant Blue R (RBBR) dye was carried out using Ulva lactuca, Codium fragile and their carbonization products; adsorption kinetics and isotherms were determined. Carbonized adsorbents were produced in a tubular furnace at the heating rate of 20˚C min-1 and temperature of 500 ˚C with a nitrogen flow rate of 300 ml min-1. Adsorption was carried out in a shaking water bath at the temperature of 25 ˚C and shaking speed of 200 rpm for 2 h. Carbonized adsorbents have been found to have greater adsorption capacity than raw biomass. It was seen that the adsorption lasted for 90 and 60 minutes for raw and carbonized adsorbents, respectively and then desorption begun. Maximum adsorption was achieved with the carbonized Ulva lactuca macroalgae (2.11 mg g-1). It has been found that the most suitable kinetic model for all absorbents was the pseudo-second-order kinetic model. The best fit of equilibrium data for all adsorbents was described by the Langmuir model.