The purpose of this study was to collect key success factors (KSFs) that determine information security management in cloud computing. Through contemporary literature reviews, we emphasized four major aspects: the external dimension, the internal dimension, the technology dimension, and the execution dimension. We used these dimensions to develop a questionnaire for collecting the responses from experts, and then used the fuzzy analytic hierarchy process (Fuzzy AHP) to categorize and analyze these responses. The investigations concluded the six major KFSs: authentication, disclosure prevention, encryption, service model, interface, and customer. Different from previous perceptions, information security management in cloud computing emphasizes factors that are more market-oriented. In addition, we explored several important KSFs, such as service model, interface, and customer criteria. These KSFs differed from the factors commonly regarded in the internet age.