The aim of this study was to measure the acceptance of a telemedical, inpatient-outpatient care concept by physicians, patients and the relatives of patients. Based on a quantitative survey of acceptance, both the potential and success factors influencing the use of telemedicine were to be highlighted. The TELnet@NRW study is a national, multicenter, cluster-randomized study in stepped-wedge design conducted from February 2017 to January 2020 for the purpose of documenting changes in the quality of care through telemedicine in an inpatient-outpatient network. Consultations were focused on intensive care medicine and infectious diseases. This current study used questionnaires for specific groups of patients to determine acceptance of the telemedical care concept practiced in the main study. The survey was anonymously conducted once in either digital or paper-based form during the reporting period. The answers of 126 questionnaires from physicians and 1686 questionnaires from patients and their relatives were evaluated. The physicians of both sectors attributed high potential (up to 88.4%) for telemedicine to improve guideline-adherent treatment. A trustworthy and appreciative communication during the telemedical consultation represented a positively reinforcing success factor. The additional workload generated by telemedicine inhibited acceptance, especially in the inpatient sector. A continuation of telemedicine beyond the end of the project was supported by the majority of surveyed physicians (inpatient 60.6%, outpatient 82.1%) as well as in patients and their relatives (inpatient 79.7%, outpatient 57.4%) in both sectors. There is widespread acceptance of telemedical, inpatient-outpatient care concepts among physicians, patients and their relatives. Low-effort processes and user-centered technology are crucial to increase the rate of use. Telemedicine has the potential to improve the quality of care and can serve as a robust component of sustainable healthcare in Germany.