In this study, the effect of particle size on sugarcane bagasse (SB) and corn silage (CS) with industrial wastewater for biogas production were investigated at a mesophilic temperature of 35 °C. Biogas, a renewable source of energy could serve as an alternative means to replace the use of non-renewables such as coal in South Africa. It has been found that the speed and stability of the anaerobic digestion process depends mainly on the particle size of the input material. Variations in particle sizes for both SB and CS were observed at 2 mm, 1 mm, 0.6 mm and 0.4 mm whiles the hydraulic retention time, the organic loading rate and the pH of the biodigesters were kept constant at 20 d, 0.5 gVS/100 mL and 6.5 - 8.0. 1 L biodigesters controlled in batch mode were used in this study leaving a 200 mL headspace followed by nitrogen purging to create the anaerobic environment. Highest biogas yield of 125 mL/d was observed from CS at a particle size of 0.4 mm. The result showed that smaller particle size distribution favours the biogas production of CS compared to SB.