There is growing recognition internationally of the importance of involving consumers, patients, and the public in research. This is being driven by political mandates for policies, funding, and governance that demand genuine and meaningful engagement with consumers. There are many potential benefits to involving consumers in research, including an increased relevance to patient needs, improved quality and outcomes, and enhanced public confidence in research. However, the current literature highlights that efforts to incorporate their contributions are often tokenistic and there is a limited understanding of the psychological factors that can impact researcher attitudes, intentions, and behaviours when working with consumers in research. To address this gap, this study conducted 25 semi-structured interviews with health researchers in Australia using the qualitative case study method. The study aim was to explore the underlying influences on researcher behaviour when involving consumers in health research. The results identified several factors that influence researchers’ behaviour, including better quality research, emotional connection and the humanisation of research, and a shift in research culture and expectations as major drivers. However, beliefs that consumers would hinder research and must be protected from risks, paternalism, and a lack of researcher skills and resources were identified as major barriers. This article presents a theory of planned behaviour for consumer involvement in the health research model. The model offers a valuable tool for policymakers and practitioners to understand the factors that influence researcher behaviours. It can also serve as a framework for future research in this area.