Chitin is one of the most abundant biopolymers widely distributed in the marine and terrestrial environments. Chitinase enzyme has received increased attention due to its wide range of biotechnological applications. Aspergillus terrus was found to be a good chitinase producer among the five fungi isolated from different soil samples from Al-Jouf city, Saudi Arabia. Maximum production of chitinase was obtained when using 2% of Shrimp-shell powder as a sole carbon source in the fermentation medium. The high level of chitinase production was observed in the culture medium with pH 5 at 30 C for five days at shaking conditions. Some properties of the crude chitinase were studied. In the present study, the antifungal activity of crude A. terrus chitinase was investigated against Apergillus niger, Aspergillus oryzae, Pencillum oxysporium, Rhizoctonia solani, Fusarium oxysporium, Rhizopus sp. and Mucor sp. and also estimated. The chitinase was found to inhibit the growth of some phytopathogenic fungi tested. The present work provides a suitable medium composition for enhancement of chitinase production by A. terrus and some properties of crude enzyme. Moreover, the study reflects the potential of A. terrus chitinase for biotechnological application.