Two potent fungicides m-Dinitro benzene and Pentachloro phenol were used to inhibit the activities of Cellulase Enzymes, elaborated by the fungus Aspergillus niger. The two fungicides exerted a depressive effect on the total counts and on the individual cellulose decomposing fungal species. When these fungicides were incorporated in the liquid culture medium, specified for growth and extracellular enzyme production by some selected fungal species, there was a significant reduction in mycelial growth as well as in cellulase production by the fungi tested. Concerning the effect of fungicides on the production of fungal enzymes, there are several reports indicating the varying effect of fungicides on both mycelial growth and extracellular enzyme production according to different factors including the kind of doses of fungicides and fungal species tested. This work was conducted to investigate the effect of two potent fungicides on the activities of Cellulase Enzymes from Aspergillus niger.