Purpose: The concept of a mental model has been described by theorists from diverse disciplines. The purpose of this paper is to offer a robust definition of an individual mental model for use in organisational management. Design/methodology/approach: The approach adopted involves an interdisciplinary literature review of disciplines, including system dynamics, psychology, cognitive science and organisational learning. Findings: Critical reflection on the published individual mental model definitions revealed similarities and shortcomings. It is argued that here the literature presents some consensus in the concept being internally held and having the capacity to affect how a person acts. The proposed definition of an individual mental model was found to be robust through a complexity based inquiry conducted in an organisation within the hospitality industry. Research limitations/implications: The application of the model has only been tested in one case study with a small staff sample in the hospitality industry. Thus generalisation is limited pending further testing. Practical implications: The pilot study demonstrated the usefulness of the definition of an individual mental model in making the conceptualisations of work practices explicit at various levels within organisations. Originality/value: This paper produces a definition that is lucid, inclusive, and specific for mental model research and knowledge management in organisations. The paper provides added value for academics and organisational practitioners interested in a robust definition for understanding the concept and the implications of mental models on an individual's actions.