Background: Cardiovascular diseases are the leading cause of death globally, causing 31% of all deaths worldwide. The Danish healthcare system is characterized by fragmented delivery of healthcare services and rehabilitation activities. In order to rectify fragmentation and improve the quality of care, the Teledialog Telerehabilitation Program for cardiac patients was developed and tested. The Teledialog program was based on the assumption that a common communication platform shared by healthcare professionals, patients and relatives could reduce or eliminate the fragmentation in the rehabilitation process and improve co-operation between the healthcare professionals. Objective: The aim of this study was to assess the interorganizational co-operation between healthcare professionals across sectors (hospitals, healthcare centers in municipalities) in a cardiac telerehabilitation program. Methods: Theories of networks between organizations, the sociology of professions and the "community of practice" approach were used in a case study of a cardiac telerehabilitation program. A triangulation of data collection techniques was used, including documents, participant-observation (n=76 hours) and qualitative interviews with cardiac patients (n=37). Data was analyzed using NVivo 11.0. Results: The following key themes were identified: (1) shared e-rehabilitation plan integrates the workflow between the organizations and reduces fragmentation, (2) a community of practice in telerehabilitation was established, and (3) the telerehabilitation program became a joint program across hospitals, healthcare centers and municipalities. Conclusions: The Teledialog Telerehabilitation Program was a new innovative cardiac telerehabilitation program that was tested in large scale across hospitals, healthcare centers and municipalities. Assessments showed that the Teledialog program and its associated technologies helped improve interorganizational cooperation and reduce fragmentation. The program helped integrate the organizations and led to the creation of a community of practice. Further research is needed to explore long-term effects of implementation of telerehabilitation technologies and programs. Trial Registration: Clinicaltrials.gov NCT01752192; https://clinicaltrials.gov/ct2/show/NCT01752192? term=NCT01752192&cntry=DK&rank=1 (Archived by WebCite at http://www.webcitation.org/6yR3tdEpb)