The effect of ultrasound technology to extract the water soluble polysaccharides from dried and milled by-products generated from Agaricus Bisporus production was studied. Amounts of β-glucan 1.01 and 0.98 g/100 g dry mass were obtained in particle sizes of 355-250 μm and 150-125 μm from the mushroom by-products. Three parameters of extraction were studied; extraction time (0-15 min), ultrasonic amplitude (20-100 μm) and precipitation time (1 or 18 h). The application of ultrasounds enhanced the extraction polysaccharide yields compared to the untreated samples. The highest extraction yield of 4.7% was achieved with an extraction time of 15 min, maximum amplitude of 100 μm with 1 h of precipitation in 80% ethanol. The coefficient of determinations for predicted water soluble polysaccharides extraction yields showed good correlation with the experimental data at the 95% confidence level and indicated that the non-exponential Peleg's model could be employed to predict the extraction polysaccharide yields after ultrasound treatment.