Background: In the Netherlands, healthcare professionals attending patients in the last phase of life, can consult an expert palliative care team (PCT) in case of complex problems. There are two types of PCTs: regional PCTs, which are mainly consulted by general practitioners, and hospital PCTs, which are mainly consulted by healthcare professionals in the hospital. Integration of these PCTs is expected to facilitate continuity of care for patients receiving care in different settings. We studied facilitators and barriers in the process of developing and implementing an integrated transmural palliative care consultation service. Methods: A multiple case study was performed in four palliative care networks in the southwest Netherlands. We aimed to develop an integrated transmural palliative care consultation service. Researchers were closely observing the process and participated in project team meetings. A within-case analysis was conducted for each network, using the Consolidated Framework for Implementation Research (CFIR). Subsequently, all findings were pooled. Results: In each network, project team members thought that the core goal of a transmural consultation service is improvement of continuity of palliative care for patients throughout their illness trajectory. It was nevertheless a challenge for hospital and non-hospital healthcare professionals to arrive at a shared view on goals, activities and working procedures of the transmural consultation service. All project teams experienced the lack of evidence-based guidance on how to organise the service as a barrier. The role of the management of the involved care organisations was sometimes perceived as unsupportive, and different financial reimbursement systems for hospital and out-of-hospital care made implementation of a transmural consultation service complex. Three networks managed to develop and implement a transmural service at some level, one network did not manage to do so. Conclusions: Healthcare professionals are motivated to collaborate in a transmural palliative care consultation service, because they believe it can contribute to high-quality palliative care. However, they need more shared views on goals and activities of a transmural consultation service, more guidance on organisational issues and appropriate financing. Further research is needed to provide evidence on benefits and costs of different models of integrated transmural palliative care consultation services.