Sodium-alginate/acrylamide (Na-alginate/AAm) cross-linked hydrogel was prepared by using gamma irradiation. The gel content and the water absorbency behavior of the obtained hydrogel were investigated. The thermal and morphological properties of the prepared hydrogel were studied using thermogravimetric analysis and scanning electron microscopy. The thermal stability of Na-alginate significantly changed when mixed with AAm. The adsorption of basic violet 7 dye on the prepared hydrogel was studied under different experimental conditions. The adsorption process for the basic dye was proven pH dependent. The maximum amount adsorbed (mg/g) of the Na-alginate/AAm for the dye was found to be 78.1.0 mg/g at pH 9.0. (c) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1899-1906, 2011