Cellulase is an essential glycosyl hydrolase enzyme, which produces glucose from cellulose hydrolysis. They have been widely used in food and feed processing, detergent, textile and biofuels production industries. The present study was undertaken to isolate, identify and screen bacteria from Omani ecosystems with high cellulase activity. Bacterial strains were isolated and identified based on 16S rRNA sequences and screened on carboxymethylcellulose (CMC) agar plate for the ability to produce cellulase enzyme. CMC and palm leaves were used as a carbon sources in the production medium and optimization of pH, temperature and various metallic ions for the activity of enzyme production was tested. Cellulase enzyme activity was measured by dinitrosilsalic acid (DNS) method. A Total of 44 bacterial strains were isolated and they mainly belonged to the genus Bacillus. Among them, four bacterial isolates (MI-1, MI-10, MI-24 and MI-42) generated the largest clear zone on CMC agar plate. These isolates were able to utilize palm leaves and produce higher cellulase activity than with CMC media. The optimum temperature and pH for the cellulase enzyme activity were found to be 50°C and 7, respectively. Moreover, cellulase activity increased in the presence of K and Na ions, while decreased in the presence of Ca, Mg, Fe, Cu and Zn ions. In conclusion, the selection of appropriate growth medium with favorable incubation conditions maximized the production of cellulase enzyme. However, different parameters should be investigated including different concentrations of ions and using other agricultural wastes.