Belgium has over two decades of experience in Health Technology Assessment (HTA), initiated by the establishment of the Drug Reimbursement Committee (DRC) in 2001 within the National Institute for Health and Disability Insurance (NIHDI). NIHDI is responsible for HTA in the context of reimbursement requests for medical products. The Belgian Health Care Knowledge Centre (KCE) performs HTAs that are not directly related to concrete reimbursement requests. KCE involves a diverse range of stakeholders in its HTAs, including patients. It took several initiatives to systematically involve patients in its work. In 2012, a study was performed to explore various patient involvement models and their acceptability to Belgian stakeholders. In 2015, representatives from four umbrella patient organisations joined KCE Board, followed by the publication of a position paper in 2019 affirming KCE’s commitment to patient involvement and a methodological guide for KCE researchers. Collaboration with umbrella organisations was further formalised in 2021, with very early patient involvement in KCE studies. Today, KCE seeks to further implement and evaluate its patient involvement methods, focusing on welcoming patients, adapting collaboration formats to accommodate patients with illnesses or disabilities, and providing systematic end-of-project feedback to ensure continuous improvement in patient involvement practices.