This article presents a new theoretical framework for coordinating an inter-unit collaborative service process towards a joint customer. To guarantee the quality and the added value of the service offering for the end customer, the two business units should organise their work as cross-functional and cross-unit business processes. The common service process is itself presented as a central coordination mechanism. It defines how tasks and responsibilities are shared between the collaborating units. The framework presents the factors supporting cooperation between the units, the prerequisites of the common service process and the ways of coordinating inter-unit cooperation. The study applies a constructive action research approach and abductive reasoning to develop the new framework through a single-company longitudinal, qualitative case study that consists of three development projects. Business unit managers can use the new framework as an analytical tool for recognising potential factors supporting cooperation and coordination in their specific operating environments.