Background: Existing evidence suggests that clinician and organisation engagement in research can improve healthcare performance. With the increase in allied health professional (AHP) research activity, it is imperative for healthcare organisations, clinicians, managers, and leaders to understand research engagement specifically within allied health fields. This systematic review aims to examine the value of research engagement by allied health professionals and organisations on healthcare performance. Methods: This systematic review had a two-stage search strategy. Firstly, the papers from a previous systematic review examining the effect of research engagement in healthcare were screened to identify papers published pre-2012. Secondly, a multi-database search was used to conduct a re-focused update of the previous review, focusing specifically on allied health to identify publications from 2012–2021. Studies which examined the value of allied health research engagement on healthcare performance were included. All stages of the review were conducted by two reviewers independently. Each study was assessed using the appropriate Joanna Briggs Institute critical appraisal tool. A narrative synthesis was completed to analyse the similarities and differences between and within the different study types. Results: Twenty-two studies were included, comprising of mixed research designs, of which six were ranked as high importance. The findings indicated that AHP research engagement appears related to positive findings in improvements to processes of care. The review also identified the most common mechanisms which may link research engagement with these improvements. Discussion: This landmark systematic review and narrative synthesis suggests value in AHP research engagement in terms of both processes of care and more tentatively, of healthcare outcomes. While caution is required because of the lack of robust research studies, overall the findings support the agenda for growing AHP research. Recommendations are made to improve transparent reporting of AHP research engagement and to contribute essential evidence of the value of AHP research engagement. Trial registration: This systematic review protocol was registered with the international prospective register of systematic reviews, PROSPERO (registration number CRD42021253461).