Abstract: Crude polysaccharides of mature fresh (FB) and dried fruiting bodies (DB) of the edible mushroom, Lentinus sp. strain RJ-2 were evaluated for their antioxidant properties. The crude polysaccharides yields in FB and DB were 115.84 and 93.66 mg g-1 dry weight mushroom, respectively. Trolox equivalent values in scavenging abilities of both crude polysaccharides against both 2, 2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radicals as well as reducing properties were in similar ranges. The crude polysaccharides contained protein, reducing sugar and phenol compounds. The results from Fourier transform infrared (FTIR) spectroscopy and Thin Layer Chromatography (TLC) suggested that the crude polysaccharide contained a monosaccharide with six carbon atoms in a pyranose ring and mannose are proposed to be the majority. This study suggested that the crude polysaccharides from Lentinus sp. mushrooms could potentially be used as natural antioxidants.