Abstract Background The Australian Mental Health Professionals Network (MHPN) is fostering a collaborative, interdisciplinary approach to mental health care through the establishment of local interdisciplinary networks of mental health professionals. This paper reports on those factors seen by MHPN participants and staff as having affected the formation and continuation of interdisciplinary networks, and therefore the likely sustainability of these groups. Method The paper draws on qualitative data from focus groups with mental health professionals participating in MHPN activities and MHPN staff. Results The findings suggest that MHPN’s approach to establishing sustainable interdisciplinary networks has been influenced by a number of factors at the micro-, meso-and macro levels. At the micro-level, factors such as clarity and structure of ongoing meetings, individual dynamics and the role of ‘champions’ can promote or constrain sustainability of ongoing networks. Those networks that had established following an initial workshop and had continued to meet as an interdisciplinary network tended to be led by well-respected co-ordinators, involve members who are enthusiastic and keen to learn from each other, have a flexible structure and meet regularly for a well-defined purpose. These features are underpinned by good communication between network members and with MHPN administration. At the meso- and macro-levels, the key issue relates to resourcing, as well as the wider policy context. Conclusions The support and practical resources provided by MHPN have been crucial in guiding successful networks as they form and continue to meet on a regular basis. The networks have also required internal leadership and support, and a clear purpose in order to form and to continue their activities. These findings are consistent with the literature, which states that sustainability of programs is reliant on factors at the project design and implementation level, as well as on factors inherent within the host organization and at the wider community level.