Many successful field cases of microbial enhanced oil recovery (MEOR) method have been reported for sandstone reservoirs. The objective of this study is to investigate the potential of MEOR method in UAE carbonate reservoirs. Two Bacillus strains were incubated at temperatures from 35 to 55°C, and their effects on crude oil properties and recovery were tested. It was discovered that neither strain could effectively reduce crude oil viscosity. Bacteria solutions were subsequently injected into a glass Hele-Shaw model to simulate microbial flooding in a fracture. It was observed that both strains grown under 45°C achieved maximum enhanced recovery of over 13%. Core flooding tests were conducted at elevated temperature of 70°C with limestone core. The two strains achieved enhanced oil recovery of more than 4.5%, respectively. The observation on core flooding test indicated selective plugging as the dominant recovery mechanism. Even though the recovery test results were positive, an analysis shows that MEOR method is not cost-effective. Therefore, MEOR technology may have limited potential in UAE carbonate reservoirs.