BackgroundGroup model building (GMB), is a qualitative focus group like study design from the field of system dynamics, that leads a group of topic experts (often key stakeholders of a problem), through a set of scripted activities to create a conceptual model of their shared view on this problems’ key contributing factors and their interactions. By offering a specific step wise approach to the complexity of a problem, GMB has provided better understanding and overview of complex problems across different scientific domains, in addition to traditional research methods. As the development of geriatric syndromes and organization of geriatric care are often complex issues that are difficult to research, understand and resolve, GMB might be a useful methodology to better address these issues. This study aimed to describe the methodology of online GMB using a geriatric case study.MethodsFour online GMB sessions were designed by two clinician researchers. A GMB methodology expert was consulted for optimal design. Scriptapedia scripts formed the core of the sessions. These scripts were adapted to the online format. Experts were recruited purposefully and included seven local health care professionals, one patient representative and one healthcare insurance data analyst. The outcome was a conceptual model of older adults’ emergency department visits, which was discussed in a separate article.ResultsDuring implementation of these four sessions, the sessions were adjusted and two extra (non-scripted) sessions were added because defining unambiguous contributing factors to the geriatric case was challenging for the experts. Paraphrasing, categorizing, iterative plenary reflection, and reserving extra time were used to help experts overcome this challenge. All sessions were held in April and May 2021.ConclusionThis study shows that GMB can help unravel complex problems in geriatrics, both pathophysiological as organizational, by creating step wise overview of their key contributing factors and interactions. Furthermore, it shows that GMB can be used by clinicians, researchers and health policy makers to better understand complex geriatric problems. Moreover, this paper can help to overcome specific implementational challenges in the geriatric field.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12877-023-04110-x.