BACKGROUND: Although guidance for primary care professionals on how to communicate with patients about health behaviour change is prevalent, the evidential base for this guidance is unclear. We aimed to systematically review the current guidance for general practice healthcare professionals on how to communicate about health behaviour change with patients, and ascertain what evidence underpins these. METHODS: In this systematic review without meta-analysis (SWiM), we searched the electronic databases MEDLINE, Embase, PsycINFO, CINAHL, Scopus, and Web of Science on 23rd June 2023. We also searched national guidelines, training, and magazines aimed at providing behaviour change communication guidance for clinicians, on 6th August 2023. Eligible sources were resources providing health behaviour change communication guidance for healthcare professionals in general practice. Two reviewers screened sources for inclusion. Once included, one reviewer extracted relevant communication recommendations from each document. For each communication recommendation, one reviewer identified the presence or absence of citations to supporting evidence. Citations were then examined and classified by relevance. The key outcome measure was the number of communication recommendations supported by evidence and relevance of the supporting evidence cited. RESULTS: Across 1163 communication recommendations identified, 677/1163 (58.2%) included one or more citations, totalling 3640 citations. Of these, 1432/3640 (39.3%) were considered relevant. Of 1163 specific communication recommendations identified, 233/1163 (20.0%) used exclusively relevant evidence sources, whilst 61 (5.2%) used exclusively irrelevant evidence sources. Four hundred thirty-one (37.0%) recommendations included at least 1 relevant citation. CONCLUSIONS: Guidance aimed at supporting healthcare professionals to communicate about behaviour change with their patients is rarely clearly substantiated with a citation to relevant supporting evidence. Where evidence is provided, it is rarely explicitly relevant to the claim in the guidance which cited it. Given that communication is fundamental to a range of crucial healthcare outcomes, guidance should draw on available evidence to better support healthcare professionals. Further research should examine the evidence underpinning other communication guidance. SYSTEMATIC REVIEW REGISTRATION: Schwarze-Chintapatla A, Livingstone-Banks J & Albury C. What evidence underpins communication guidance regarding behaviour changes for healthcare professionals within general practice: A systematic review. PROTOCOL: Open Science Framework (2024).