Working relationships are important in effecting project performance and cooperation is believed to be a behavioural consequence of trust. Trust, being a quality of relationships, involves people interacting at interpersonal and inter-firm levels. This is investigated through 10 partnering and non-partnering projects, using a validated trust scale. A case study approach is used to collect qualitative data through a quantitative approach to help understand the concept of trust. Data were collected from clients, contractors, consultants and subcontractors. Clients and contractors have a tendency to trust individuals whereas contractors and subcontractors have a tendency to trust firms. Inter-firm trust is better understood than interpersonal trust; but both are associated with keeping commitments and demonstrating cooperation, even though interpersonal trust is considered more important. Partnering does not necessarily exhibit more trust than non-partnering projects whereas clients and contractors have different emphasis on interpersonal and inter-firm trust. Therefore, to promote trusting relationships in multi-parties is to fulfil not only the technological and economical goals, but also the moral and social goals as expressed in people relationships such that a socially safe working place can be created. For this reason, middle managers need to know about trust because they face more relationship problems than others.