Enzymatic hydrolysis of pretreated (acid + autoclaving) and delignified (alkali + ultrasound) P. hysterophorus ICG001 was carried out under sonication. Ultrasound assisted enzymatic hydrolysis of P. hysterophorus gave sugar concentration of 27.6 ± 1.1 g/L with a yield of 711.34 mg/g of delignified biomass (293.23 mg/g of raw biomass). The sugar yield in this study was higher than those from other reports such as in a study by Pandiyan et al. (2014) enzymatic hydrolysis of acid, alkali and biologically pretreated Parthenium sp. biomass using Accellerase® 1500 (endoglucanase 2200 CMC IU/g + β-glucosidase 525 pNPG IU/g + xylanase 115 IU/g) resulted in sugar yield of 476.0, 513.0, 410.0 mg/g of pretreated biomass, respectively. In another study by Rana et al. (2013), a sugar yield of 485.64 mg/g of pretreated biomass was achieved after enzymatic hydrolysis of biologically (Trametes hirsuta) pretreated Parthenium sp. using Accellerase® 1500 (endoglucanase 2200 IU/g + β-glucosidase 525 IU/g). However, in the above mentioned studies ( Rana et al., 2013 and Pandiyan et al., 2014) the enzymatic hydrolysis was not performed under ultrasound. Similar or even higher sugar yields in enzymatic hydrolysis in our study that has used crude cellulase enzyme obtained from natural isolate, as compared to the studies reported in literature with purified commercial enzymes, essentially show that lesser activity of the hydrolysis enzyme could be compensated by the physical effects of strong micro-convection induced by ultrasound.