Biosorption of heavy metals can be an effective process for the removal and recovery of heavy metal ions from aqueous solutions. The biomass of marine macroalgae has been reported to have high uptake capacities for a number of heavy metal ions. In this paper the adsorption properties of a pretreated biomass of macroalga Durvillaea potatorum for Ni2+ were investigated. Adsorption isotherms and kinetics were obtained from batch adsorption experiments. The adsorption capacities were pH dependent and a maximum adsorption capacity was obtained to be 1.13 mmol/g at a pH of about 6. A modified Langmuir model was proposed for the correlation of pH-dependent isotherms. The adsorption process was fast; 90% of adsorption occurred within 25 minutes and equilibrium was reached at around 1 hour. Light metal ions at a concentration of 10 mM did not affect Ni2+ adsorption significantly. Fixed-bed breakthrough curves for Ni2+ removal were also obtained. This study demonstrated that the pretreated biomass of D. potatorum can be used as an effective biosorbent for the treatment of Ni2+-containing wastewater streams.