Purpose: An innovation network, called the Pasture Improvement Leadership Group (PILG), was formed to improve the quality and consistency of advice provided to dairy farmers in New Zealand, after they expressed dissatisfaction with their pastures. The aim of this paper is to better understand the challenges of forming and maintaining networks to coordinate advisory services, with a focus on the dynamics between public and private sector actors. Methodology: The concept of innovation networks is used to describe the PILG, as well as to diagnose the effectiveness of the PILG, and to identify and discuss critical success factors for the development of an innovation network involving public and private sector actors. Findings: Six critical success factors were identified, such as: a sense of urgency and willingness to work together; sharing a common vision; a broad representation of the involved or affected stakeholders; and having a neutral innovation broker. Challenges remain around the level of interaction and the different incentives of public and private sector actors. Theoretical implication: This work suggests that not only the formation of an innovation network requires careful consideration regarding the purpose, governance, and the type of actors involved, but that the maintenance of an innovation network is equally important. Practical implication: The results have been influential within DairyNZ, providing evidence that innovation networks are effective and consequently are being applied more widely in the New Zealand dairy industry. Originality/Value: This is the first New Zealand study into the development of innovation networks aimed at collaboration between public and private sector actors in a highly privatised extension system and contributes to the emerging body of work on coordination in pluralistic extension systems.