Background: New methods for prevention and health promotion and are constantly evolving; however, positive outcomes will only emerge if these methods are fully adopted and sustainable in practice. To date, limited attention has been given to sustainability of health promotion efforts. This study aimed to explore facilitators, barriers, and requirements for sustainability as experienced by professionals two years after finalizing the development and implementation of a multisectoral child health promotion programme in Sweden (the Salut programme). Initiated in 2005, the programme uses a ‘Salutogenesis’ approach to support health-promoting activities in health care, social services, and schools. Methods: All professionals involved in the Salut Programme’s pilot areas were interviewed between May and September 2009, approximately two years after the intervention package was established and implemented. Participants (n = 23) were midwives, child health nurses, dental hygienists/dental nurses, and pre-school teachers. Transcribed data underwent qualitative content analysis to illuminate perceived facilitators, barriers, and requirements for programme sustainability. Results: The programme was described as sustainable at most sites, except in child health care. The perception of facilitators, barriers, and requirements were largely shared across sectors. Facilitators included being actively involved in intervention development and small-scale testing, personal values corresponding to programme intentions, regular meetings, working close with collaborators, using manuals and a clear programme branding. Existing or potential barriers included insufficient managerial involvement and support and perceived constraints regarding time and resources. In dental health care, barriers also included conflicting incentives for performance. Many facilitators and barriers identified by participants also reflected their perceptions of more general and forthcoming requirements for programme sustainability. Conclusions: These results contribute to the knowledge of processes involved in achieving sustainability in health promotion initiatives. Facilitating factors include involving front-line professionals in intervention development and using small scale testing; however, the success of a programme requires paying attention to the role of managerial support and an overall supportive system. In summary, these results emphasise the importance for both practitioners and researchers to pay attention to parallel processes at different levels in multidisciplinary improvement efforts intended to ensure sustainable practice change.