Cellulase enzymes have versatile industrial applications. This study was directed towards the isolation, production, and characterization of cellulase enzyme system. Among the five isolated fungal cultures, Emericella variecolor NS3 showed maximum cellulase production using untreated orange peel waste as substrate using solid-state fermentation (SSF). Maximum enzyme production of 31 IU/gds (per gram of dry substrate) was noticed at 6.0 g concentration of orange peel. Further, 50 A degrees C was recorded as the optimum temperature for cellulase activity and the thermal stability for 240 min was observed at this temperature. In addition, the crude enzyme was stable at pH 5.0 and held its complete relative activity in presence of Mn2+ and Fe3+. This study explored the production of crude enzyme system using biological waste with future potential for research and industrial applications.