Shifting freight transport from roads to more energy-efficient modes of sea and rail, i.e., a modal shift, is essential to reducing emissions from transport. Two actors influencing the rate of transition to such modes are logistics service providers (LSPs) and shippers. In their relationships, power and trust are vital interorganisational factors that need to be managed. The purpose of this paper is to examine how the existence and use of power and trust and their interplay can facilitate a modal shift in the ongoing relationships between shippers and LSPs. The research is based on an in-depth qualitative case-study of two cases, each consisting of the relationship between a retailer and an LSP. Empirical data was collected through semi-structured interviews, and the analysis was guided by three dimensions of power (resources, processes and meaning) and three types of trust (contractual, competence and goodwill). The results show that power and trust do, indeed, exist and influence modal shift solutions in shipper–LSP relationships. Alignment between shippers and LSPs is found to be vital in terms of the perceptions and values needed to strengthen the power of meaning, and in terms of the processes and participation needed to strengthen the power of processes. Trust is a facilitating factor in both instances, and it also works as a mediating factor in any asymmetry between the power of shippers' resources and LSPs. © 2022 The Authors