Nowadays, Public Sector Innovation is high on government agendas across OECD countries. Confronted with major budgetary pressures and grand societal challenges, governments worldwide experience a need to step beyond conventional wisdoms and sedimented practices. Despite the growing awareness of the need for collaboration, there is a lack of knowledge about how such collaborative governance arrangements results in meaningful innovations regarding policies and services, and how different forms of collaborative governance interact and reinforce each other. Also it is unclear what organisational and individual conditions need to be present within administration to foster collaborative governance arrangements. PSI-CO will address this research gap by conducting a multi method study on collaborative innovation, studying both how collaborative governance can foster innovation, and by what conditions, in turn, collaborative innovation is supported. Next to providing academic advances, research on this topic is of particular relevance to the federal ministries and agencies who are looking for and experimenting with innovation strategies. It will offer practitioners insight into the potential of promoting public sector innovation through collaboration within and across governments and with external stakeholders, and provide guidelines for establishing conditions favourable for such collaborative innovation. The overall research question of this project is ‘how and under which conditions do collaborative governance arrangements foster the initiation, adoption and diffusion of innovations in policies and services?’