Selecting an appropriate cloud service provider (CSP) is one of the most important challenges affecting sourcing performance. Although cloud computing (CC) relies on the principle of information technology outsourcing (ITO), it remains unclear if selection criteria for ITO provider hold true. Hence, the purpose of this research is to identify the most important criteria for the selection of cloud service providers (CSP). We do this by conducting a Delphi study which includes 16 cloud service decision makers across different cloud service models, company sizes, and industry types. Our results show consensus on CSP selection criteria and identify functionality, legal compliance, contract, geolocation of servers, and flex-ibility as top five CSP selection criteria. From a theoretical perspective, we demonstrate that results from ITO research hold true for CC research as differences in delivery model and arrangement between ITO and CC will be considered. Practitioners like CSP and cloud decision makers get guidance from our findings to conduct optimal cloud service investments. This is the first study which provides a com-prehensive view on relevant criteria for CSP selection.