Although academic interest for patient involvement in health research decision-making is growing, in practice it proves challenging to involve patients meaningfully and sustainably. This article aims to unravel systemic factors influencing the embedding of meaningful patients' involvement in proposal appraisal at a private cancer research funding organization. In the case study, the emergent and participatory research approach Reflexive Monitoring in Action was applied. At first, a positive stance of stakeholders towards patient involvement was accompanied by a lack of tools and structures. This lack of tools led to the execution of various interventions. Analysis reveals that structural interventions succeeded in the bureaucratic context. The required cultural shift was also addressed, but took longer to materialize. This may have reduced the meaningful involvement of patients in proposal appraisal in practice. To overcome the underlying systemic barriers, an approach is needed that encourages stakeholders' reflexivity in the structural, cultural, and practical domain.