Cellulase enzymes were produced by Alternaria sp. MS28 when grown in cellulose media. The fungus made different types of cellulases depending on the temperature it was grown at. Endoglucanase was produced when the fungus was exposed to CMC, while β-glucosidase was made in the presence of salicin. Glucose, however, inhibited cellulase production. The enzymes were most active in specific temperature and pH conditions. The study showed that the production of these enzymes was influenced by the type of substrate present in the media.