Structured abstract:Purpose -The study compares the coordination of supply chain networks in contractually different complex construction projects. Design/methodology/approach -A comparative case study of the coordination of collaborative work in two successful hospital construction projects was conducted. One of the projects applied multiple dyadic contracts, whereas the other project applied one multiparty contract between the parties. The projects were located in the USA. Data was collected by observing the coordination on the construction sites for six weeks and by conducting 72 interviews. Findings -The paper shows that depending on the contract type, the timing and extent of complementary procedural coordination differs during projects. Compared with one multiparty contract, the multiple dyadic contracts needed to be complemented during the design phase with three additional procedural coordination mechanisms: 1) organizational design, 2) processes for collaborative work, and 3) integrated concurrent engineering sessions. Additionally, common rules of conduct were taken into use during the construction phase. However, regardless of the contract type, procedural coordination mechanisms, such as colocated working, collaborative decision making in inter-organizational meetings, a liaison role, and shared project goals were needed throughout the projects. Practical implications -If multiple dyadic contracts are applied, procedural coordination mechanisms have to be co-created by all supply chain parties at the beginning of the project. Originality/value -The study provides understanding on successful contractual and complementary procedural coordination mechanisms of supply chain networks in complex construction projects.