Challenges involving economic, environmental, and societal aspects necessitate organisations in business networks to collaborate. The scientific problem central to this paper is the difficulty of building sustainable collaborations. The research question is how to support organisations in building sustainable collaborations in their business relationships. This paper presents a new socio-technical approach to this end, i.e., PDPS (an acronym for Participatory Design of Participatory Systems) and explores its potential in a case study. PDPS is a value-based approach to the participatory design of participatory systems. Such socio-technical systems enable people working in different disciplines, departments, and organisational levels to create sustainable relationships supported by distributed information and communication technology. In a participatory system, participants gain trust, engagement, and empowerment to self-organise actions that produce results they could not have achieved alone. Following PDPS, participants collectively explore challenges in their relationship, define a joint value-based mission, and create a continuous process of self-organisation to fulfil this mission. In a case study, PDPS supported two Dutch business partners in solving recurring transport and logistics issues in retail store refurbishment projects. Turning their traditional business processes into participatory ones led to new solutions for sustainable transport and logistics, more joint business, and more profit. PDPS differs from other approaches in its involvement of all participants in a business relationship, its focus on shared values, and its capacity for creating a continuous process of self-organisation to fulfil a joint mission. This paper may support researchers, practitioners, and organisational policymakers interested in building sustainable collaborations in business networks.