The NHS is increasingly turning to the independent sector, primarily to alleviate elective care backlogs. However, implications for the healthcare system, patients and staff are not well understood. This paper provides a rapid narrative review of research evidence on NHS-funded elective care in the independent sector (IS) and the impact on patients, professionals, and the health care system. The aim was to identify the volume and evaluate the quality of the literature whilst providing a narrative synthesis. Studies were identified through Medline, CINAHL, Econlit, PubMed, Web of Science and Scopus. The quality of the included studies was assessed in relation to study design, sample size, relevance, methodology and methodological strength, outcomes and outcome reporting, and risk of bias. Our review included 40 studies of mixed quality. Many studies used quantitative data to analyse outcome trends across and between sectors. Independent sector providers (ISPs) can provide high-volume and low-complexity elective care of equivalent quality to the NHS, whilst reducing waiting times in certain contexts. However it is clear that the provision of NHS-funded elective care in the IS has a range of implications for public provision. These surround access and outcome inequalities, financial sustainability and NHS workforce impacts. It will subsequently be important for future empirical work to incorporate these caveats, providing a more nuanced interpretation of quantitative improvements.