Mobility-as-a-Service (MaaS) is a new mobility concept that allows users to plan, book and pay for a multimodal and seamless trip in a single application. Real-life examples of MaaS propositions are still scarce and most have not left a trial or pilot phase. The MaaS-team of the Ministry of Infrastructure and Water Management (IenW) wants to steer the development of the nascent MaaS market in the Netherlands and make MaaS have a sustainable impact. To this end, the MaaS-team has set up a framework agreement and seven national pilots. Within this context potential business models for MaaS proposition and their sustainability have been investigated. Through academic literature, a conceptual model is created to guide data gathering and analysis. Thirteen anonymous MaaS Service Providers (MSPs) are interviewed in semi-structured interviews from which the qualitative data is analysed through open coding. This yielded a range of target customers, value propositions and revenue and pricing models as well as results on how MSPs interact with transport operators and how they implement key functionalities. Analysis shows there is no strong business model for consumers yet. Business models aimed at the government, employers, other MSPs and other businesses seem much stronger. Additionally, business models for MaaS seem overly reliant on kickback fees. To judge whether business models for MaaS that are currently being developed are sustainable, these business models were investigated for their ability to both create and capture sustainable value. The business models are less ecologically sustainable than MSPs think they are, with little over half being ecologically sustainable. Reversely, the business models were more socially sustainable than the MSPs thought they were, with about three-quarters being socially sustainable. There thus seems to be a disconnect between perceived and actual sustainability among MSPs. Nonetheless, all MaaS propositions offer the tools to make a sustainable impact if an outside actor is willing to pay for that, allowing the MSP to capture the created sustainable value. Based on these findings the conceptual model was revised, policy and managerial recommendations are made and implications for the literature is discussed. Finally, the limitations to this research are discussed and future avenues for research are presented.