At present, many policymakers and practitioners are searching for actions that could facilitate Mobility as a Service (MaaS) developments. A potential action, which has received a lot of attention, is to introduce Intermediary MaaS Integrators; that is intermediate actors that assemble the offerings from Transport Service Providers (TSPs) and distribute these to MaaS Operators. However, little is known about if and how TSPs and MaaS Operators would appreciate the introduction of Intermediary MaaS Integrators. To address this knowledge gap, this paper explores an attempt to establish a national Intermediary MaaS Integrator in Sweden. The contribution to transportation research is twofold. Firstly, the paper advances the conceptual understanding of Intermediary MaaS Integrators by identifying four defining dimensions: Activities, Management, Processes and Context. Secondly, it deepens the knowledge of Intermediary MaaS Integrators’ value propositions by detailing TSPs’ and prospective MaaS Operators’ hopes and fears vis-à-vis them. Lastly, practical implications for how to facilitate acceptance and adoption are proposed. Intermediary MaaS Integrators should only be introduced if basic incentives for using their services are in place, and if introduced, they should preferably: go beyond offering technical services; have clear, declared objectives; be impartial and capable actors; and carefully consider their launch strategies.