Cloud-based digital transformation is having a profound impact on new and incumbent information technology service providers. In transitioning from traditional to cloud-based service provision, some IT service providers are experiencing substantial difficulties in realizing effective business models. Taking the perspective of 20 large business model mature and small and medium enterprise bornon-the-cloud multinational IT service providers, this focus group study contributes to the dearth of research examining the broader impact of cloud computing on IT service providers' business model. The study provides two core insights. First, using the STOF business model framework, the paper provides a vivid contextual understanding of the nuanced impact of cloud computing along four core business model domains: service, technological, organisational and financial. Second, the study identifies a number of salient challenges which are impacting IT service providers' efforts to effectively leverage the benefits of cloud-based digital transformation.