THE CRUDE extract activity was tested in the present study for some enzymes of Trichoderma harzianum, immobilized on polyester cloth films against the postharvest black mold disease of tomato fruit caused by Alternaria alternata. Firstly, the antifungal activity of T. harzianum against A. alternata was examined by the dual culture method using PDA plates, as it clearly inhibited the linear growth of A. alternata where the inhibition percentage was 66.5%. The hyphal interactions between both fungi were explored microscopically where hyphae of T. harzianum penetrated inside the hyphae of A. alternata then lysed them. The lysis of pathogenic cells was referred to the presence of cellulase, chitinase and glucose oxidase enzymes of T. harzianum. These enzymes were assayed quantitatively; then immobilized separately on sterile polyester films where their activity and stability were estimated in both crude cell free filtrates and saturated films. The immobilization of the tested enzymes on the polyester films showed promising findings in raising the enzyme persistence. In the meantime, these enzymatic polyester films were tested as tomato fruit coverage against the postharvest black mold disease at room temperature for 15 days. The cellulase films showed promising results, where they completely lowered the disease incidence to 0% after 4 and 7 days while it recorded 33.3 and 100% after 10 and 15 days, respectively.