Background/Aims: Collaboration, through multiple complex relationships between families and professionals, is integral to early intervention practice for children with developmental disabilities. The purpose of this study was to explain the processes involved from the multiple perspectives of all those involved in the team.Methods: A grounded theory methodology was used. The sample included five young children with developmental disabilities, six parents and 17 professionals from an early intervention team. In total, 31 interviews were carried out. Through an iterative approach to data analysis, the processes of the early intervention relationship were explored.Results: The process of the early intervention relationship emerged from the data. The relationship process happens through an overlapping five stage developmental trajectory which includes: 1) initiating, 2) experimenting, 3) intensifying, 4) integrating and 5) transitioning.Conclusions: The role of relationships between professionals, children and their parents in successful early intervention disability services is paramount. The early intervention relationship is a complex interdependent one which requires a road map of explicit stages, which can facilitate all involved in the relationship to work together. This study provides this road map in the form of a developmental relationship trajectory. Understanding the key factors, within each stage of the developmental trajectory, supports positive relationships between professionals, children and their families, thus positively influencing the outcome of early intervention practice for children with developmental disabilities.