BACKGROUND:Allied health assistants (AHAs) are support staff who complete clinical and non-clinical tasks under the supervision and delegation of an allied health professional. The effect of allied health professional delegation of clinical tasks to AHAs on patient and healthcare organisational outcomes is unknown. The purpose of this systematic review was to investigate the effect of allied health professional delegation of therapy to AHAs on patient and organisational outcomes. METHODS:A systematic review and meta-analysis was conducted. Databases MEDLINE (Ovid), Embase (Ovid), Informit (all databases), Emcare (Ovid), PsycINFO (Ovid), Cumulative Index to Nursing and Allied Health Literature [CINAHL] (EbscoHost) and the Cochrane Database of Systematic Reviews were searched from earliest date available. Additional studies were identified by searching reference lists and citation tracking. Two reviewers independently applied inclusion and exclusion criteria. The quality of the study was rated using internal validity items from the Downs and Black checklist. Risk ratios (RR) and mean differences (MD) were calculated for patient and organisational outcomes. Meta-analyses were conducted using the inverse variance method and random-effects model. RESULTS:Twenty-two studies met the inclusion criteria. Results of meta-analysis provided low quality evidence that AHA supervised exercise in addition to usual care improved the likelihood of patients discharging home (RR 1.28, 95%CI 1.03 to 1.59, I2 = 60%) and reduced length of stay (MD 0.28 days, 95%CI 0.03 to 0.54, I2 = 0%) in an acute hospital setting. There was preliminary evidence from one high quality randomised controlled trial that AHA provision of nutritional supplements and assistance with feeding reduced the risk of patient mortality after hip fracture (RR 0.41, 95%CI 0.16 to 1.00). In a small number of studies (n = 6) there was no significant difference in patient and organisational outcomes when AHA therapy was substituted for therapy delivered by an allied health professional. CONCLUSION:We found preliminary evidence to suggest that the use of AHAs to provide additional therapy may be effective for improving some patient and organisational outcomes. REVIEW REGISTRATION:CRD42019127449.