The removal of dyes from wastewater is crucial and considered an environmental challenge. Biosorption is an alternative technology to conventional processes aiming at the removal of toxic metals and dyes from polluted waters. In this study, Cystoseira barbata (Stackhouse) C. Agardh was used to remove the methylene blue (MB) from aqueous solution. The effects of solution pH, contact time and initial MB concentration at different temperatures were investigated. The adsorption reached to equilibrium in 25 min and the pH did not have an important role on the biosorption. The Freundlich isotherm model showed slightly stronger correlation than Langmuir isotherm model especially at 25 degrees C. The maximum adsorption capacity (q(m)) increased in parallel to the rise of temperature and reached to 14.97 mg/g at 45 degrees C. C. barbata can be successfully used for the removal of MB from aqueous solution.