The vision of the Physical Internet (PI) involves both sharing logistics resources and information exchange within an open network. The implementation of PI is seen as a promising contribution toward sustainable logistics. This paper investigates motives for and success factors in collaborating in a PI network. We apply an interpretive case-based research approach involving four shippers and three logistics service providers (LSPs) that operate in a PI network. Motives are defined as the reasons that encourage an organization to enter the PI network. Success factors are conditions required for organizations to continue collaborating in a PI network. This is the first PI study conducted in a multi-industry context. The findings demonstrate the central and neutral orchestration of resources (i.e., physical, digital/intangible, and relational resources) as a substantial and multi-faceted issue in PI and continuous PI collaboration. A well-accepted theory (Resource-Based View) and its most recent extension (Resource Orchestration Theory—ROT) frame and guide our research. ROT informs the deployment of physical, digital/intangible, and relational resources by a neutral orchestrator in a PI network. The knowledge of motives and success factors allows the development of future user-oriented PI services that are likely to be accepted by shippers and LSPs.