The treatment of multimorbid patients confronts physicians with special challenges. Complex disease correlations, insufficient evidence, lack of interdisciplinary guidelines, limited communication between physicians of different specialties, etc. complicate the treatment. To improve the present care situation for multimorbid patients we describe a development approach for an interdisciplinary Electronic Health Record (EHR). As part of the Dent@Prevent project, which aims to improve the intersectoral care of patients with correlating dental and chronic systemic diseases, the proposed EHR will first be tested in the field of dentistry and general medicine. Based on the HL7 FHIR standard the proposed EHR uses a modern three-tier (client-server) architecture. Crucial element of the EHR is a knowledge base, which comprises components for mapping diseases with their complex correlations, integrates patient reported parameters and classifies information in evidence levels. Using the FHIR standard the described elements need to be transferred into the data schema of FHIR resources. The development of an EHR to improve the treatment of multimorbid patients needs to be tailored to the specific needs of multimorbid patients. An interdisciplinary EHR offers the potential to facilitate communication between patients and physicians and provide them with evidence-based information on disease correlations. The next step is to test the practical implementation and applicability for further interdisciplinary disease correlations.