Inter-organizational collaboration within the construction industry consists of both engineered and emerged aspects. Engineered formal practices and emerged informal practices interplay in their influence on the overall success of client-contractor collaboration. This interplay has been recognized but is still understudied and requires further research to increase the understanding of how the interplay functions. To enable the study of the emerged aspects of collaboration we applied a practice-based approach in a longitudinal multiple case study, including four projects for operation and maintenance of road infrastructure. This paper contributes to the literature on collaboration in construction by providing detailed examples of how the interplay between engineered and emerged collaboration may unfold, showing how formal and informal practices contribute to the development of vicious and virtuous cycles of collaboration. Furthermore, our findings indicate that a virtuous cycle of only informal practices can become a weakness if unexpected problems occur. Project managers should therefore be encouraged to implement formal collaboration, even if the project team is already in a virtuous cycle of informal collaboration.