This study aims to produce Cellulase Enzyme using Trichoderma reesei and to characterize the same. The development of the cellulase enzyme production medium (CEPM) was started by varying the nitrogen source. Five different nitrogen sources tryptone, soya, yeast, casein and peptone were tested for maximum cellulase activity. Soya was found to produce more cellulase activity. Five different carbon sources namely, cellulose, glucose, potato starch, corn starch and starch were tested for maximum activity. Potato starch was found to produce more cellulase activity. Varying concentrations of soya i.e., from 1% - 5% were then tested. Maximum cellulase activity was seen with 5% soya. Varying concentrations of potato starch from 1% - 5% were then tested. Maximum cellulase activity was seen with 5% potato starch. The effect of pH and temperature on the cellulase activity was also studied. The molecular weight of the cellulase produced was found by running an SDS-PAGE. Two prominent bands were obtained, one at 40kDa and the other at 30kDa. The cellulase activity was also seen using the double layer assay procedure (Congo red plate assay).