Extended nursing roles have existed since the 1940s. The first specialist nurse for Parkinson’s disease, a complex neurodegenerative disease, was appointed in the United Kingdom (UK) in 1989. A review was undertaken using MEDLINE and Cumulative Index to the Nursing and Allied Health Literature (CINAHL), relating to the role and evidence for Parkinson’s disease nurse specialists (PDNSs). PDNSs fulfil many roles. Trials of their effectiveness have failed to show a positive benefit on health outcomes, but their input appears to improve the wellbeing of people with Parkinson’s. Now embedded in the UK Parkinson’s multidisciplinary team, this care model has since been adopted widely, including successful dissemination of training to countries in Sub-Saharan Africa. The lack of evidence to support the benefit of PDNSs may reflect an insufficient duration and intensity of the intervention, the outcome measures selected or the need to combine PDNS input with other evidence-based interventions. Whilst the current evidence base for their effectiveness is limited, their input appears to improve subjective patient wellbeing and they are considered a vital resource in management. Better evidence in the future will support the development of these roles and may facilitate the application of specialist nurses to other disease areas.