In this work, we deal with galactomannan from seeds of Cassia fistula. Galactomannan widely use to improve and develop the products in various industries. It is linear polysaccharide having a backbone of -14 linked D-mannose residues. To this chain, single alfa-D-galactose residues are linked by C-1 through a glycosidic bond to C-6 of mannose. The physicochemical and viscoelastic properties of galactomannan were here investigated. The results showed that the mannose to galactose ratios were 3.35 and 3.54 for crude and purified galactomannans, respectively, while their intrinsic viscosities at 20oC were 11.55 and 12.03 dl/g for crude and purified galactomannans, respectively. Then, the rheological properties of galactomannan solutions at different concentrations from 0.6 to 3.4 %wt were analyzed using a Haake Rheometer RS75, equipped with C35Ti sensor at 20oC. The frequency sweeps for galactomannan solutions show the typical shape for macromolecular solutions. The cross-over frequency decreased as galactomannan concentration increased.