The present investigation deals with cytochemical and chemical characterization of the main Caesalpinia ferrea seed polysaccharide. The seeds presented a water barrier tegument built by palisade cells above sclereids. It was possible to observe an endosperm highly stained by the PAS reaction, which indicates the presence of a cell wall polysaccharide. The seed polysaccharide, nearly 9% of the seed weight, was studied by 2D NMR, spectroscopy revealing that it is a galactomannan type polysaccharide with a mannose/galactose ratio of 2.65. The flow curves for 1 and 0.8% of galactomannan solutions exhibited pseudoplastic behavior especially at lower shear rate. Due to its mannose/galactose ratio and rheological behavior C. ferrea gallactomannan could be a useful polysaccharide for food industry.