This study deals with the coagulation potential of alginate extracted from marine algae Sargassum sp. for the removal of sulphur black dye from its aqueous solution. The alginate extraction was found to be efficient (44.8%) and the extracted alginate was characterized by Fourier transform infrared spectroscopy and Scanning electron microscopy techniques. Batch experiments (coagulation test) were performed to investigate the effect of alginate dose (10-60 mg/L), calcium dose (1-6 g/L) and initial dye concentration (50-250 mg/L) on dye removal. The maximum dye removal (98.2%) was achieved under the optimal conditions of the initial dye concentration 200 mg/L, Calcium dose 6 g/L, and alginate dose 30 mg/L. The kinetics study for the coagulation process was carried out and found that it suitably fits in second-order kinetics model. The literature on application of algal alginate for various wastewater treatment methods were compared with the present study and the results obtained revealed that the alginate from Sargassum sp. can be used as an efficient coagulant for the removal of sulphur black dye. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1427-1434, 2015 © 2015 American Institute of Chemical Engineers Environ Prog.