Biosorption of Cu(II) and Co(II) ions from aqueous solutions by cystoseira indica biomass was investigated in single metal systems as a function of initial pH, initial biomass concentration and temperature. The optimum biosorption conditions were studied for each metal separately. The kinetics and equilibrium of biosorption were examined in detail. three kinetic models (pseudo-first order, pseudo-second order and Weber–Morris intraparticle diffusion rate) were used to correlate the experimental data and to determine the kinetic parameters. The results indicated that biosorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters were determined at three (25, 35 and 45 oC) different temperatures by plotting lnKL versus 1/T. The ΔHo and ΔGo values of Cu(II) and Co(II) biosorption on C. indica show endothermic heat of biosorption; higher temperatures favor the process. Three well-known biosorption isotherms were chosen to describe the biosorption equilibrium. The experimental data were analyzed using Langmuir, Freundlich and Temkin isotherm model so that, the Langmuir and Temkin isotherm proposed model fits successfully the Cu(II) and Co(II) experimental data, respectively. Also Simultaneous biosorption of Cu(II) and Co(II) and onto C. indica from binary mixtures was investigated. Equilibrium studies were carried out in binary mixtures in which Cu(II) and the second metal ion concentration was varied between 25 to 300 mg/L, respectively. Results showed that both components of the binary mixture exert a synergistic effect on each other. The best fit for Cu(II) –Co(II) experimental data was provided by the Extended-Freundlich isotherm model.