Purpose Third-party logistics providers (3PLs) have significantly evolved during the last decades, yet their role within a supply chain triad has been overlooked; this study examines empirically the 3PLs' role using four established theories: resource-based view, social capital perspective, agency theory and transaction cost economics.Design/methodology/approachThis study examines the role of 3PLs in four supply chain triads, using the case study approach. Sources of evidence include interviews and secondary data.FindingsThe 3PL had different roles in multi-demand triads as service developer, customer adaptor and customer developer. The 3PL, by offering advanced services, became a service developer. The 3PL as a customer adaptor offered customised services and gain the client's trust. As a customer developer, the 3PL acted on behalf of its client in expanding its operations and meeting competitive needs.Research limitations/implicationsThe results of the case study methodology can only be generalised to similar types of 3PL. Supply chain triads are an emerging research field; theories like the resource-based view and transaction cost economics are established in the dyadic context and require further elaboration when applied in triadic contexts.Practical implicationsThe findings provide practical insights into the role that 3PL can play in supply chain triads, how they can upgrade their role by long-range planning and extending their services to create supply chain efficiency.Social implicationsUnderstanding the 3PL's role in triads can improve how companies and economies respond to crises like the recent pandemic outbreak.Originality/valueIt uncovers three different 3PL roles in supply chain triads by using four established theories.

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