Aim: To identify activities performed by Nursing Assistants in acute and primary healthcare. Design: Systematic review. Data sources: The databases MedLine/PubMed, ProQuest and Google Scholar were searched for empirical studies published in the English language between 2008 and 2018 that addressed the work of Nursing Assistants. Review methods: From an initial yield of 2,944 publications, 71 publications were retained for full text review and 20 publications included in this review. Activities undertaken by Nursing Assistants from eight countries were extracted and categorized into one of six categories. Results: Over 200 activities were identified as being delegated to Nurse Assistants globally. Many of these activities are beyond the training of the Nurse Assistant and are being performed with limited Registered Nurse supervision. Conclusion: Patient safety is at risk. Nurse Assistants' roles vary widely, with some seeing their role as similar to that of a regulated nurse, while recognizing their need for additional training. Impact: Over 31% of activities delegated to Nurse Assistants require skill and comprehension beyond their level of training. Patients and regulated nurses need to have confidence that Nursing Assistants responsible for care provision are appropriately trained and practicing within regulatory standards.