202Cellulases are a group of hydrolytic enzymes that are capable of releasing soluble sugars from lignocellulosic materials which provide a platform for a wide range of applications. The sole objective of the present investigation was strain improvement of Aspergillus niger for the enhancement of production of cellulases. The spores of A. niger were subjected to mutation by exposure to ultraviolet (UV) radiation and chemical treatment with Ethyl Methane Sulfonate (EMS). The percent survival of spores was measured after the exposure of spores to mutagenic agents. The survival percentage of spores to physical mutation and chemical mutation was between 10–90% and 10–20%, respectively. The mutants generated were screened on carboxy- methyl cellulose—congo red plates on the basis of clear zone formation in comparison with wild type A. niger. The potential mutant—EMS5 enhanced cellulase production over the parent/wild type strain on a combination of lignocelluloses (rice bran + wheat bran) at equal proportion in Solid State Fermentation (SSF) by 30–50% and was further optimized for different factors—carbon source, nitrogen source, temperature, moisture content, and inoculum density. The mutant—EMS5 yielded 50.16, 24.20, and 35.60 U/g of Filter Paper Activity (FPase), carboxymethylcellulase (CMCase), and β-glucosidase under optimized conditions in SSF.