BACKGROUND: This review, commissioned by the World Health Organization (WHO), examined the effectiveness of the WHO 6-step hand hygiene (HH) technique in reducing microbial load on hands and covering hand surfaces, and compared its effectiveness to other techniques. METHODS: Medline, CINAHL, ProQuest, Web of Science, Mednar, and Google Scholar were searched for primary studies, published in English (1978-February 2021), evaluating the microbiological effectiveness or hand surface coverage of HH techniques in healthcare workers. Reviewers independently performed quality assessment using Cochrane tools. The protocol for the narrative review was registered (PROSPERO 2021: CRD42021236138). RESULTS: Nine studies were included. Evidence demonstrated that the WHO technique reduced microbial load on hands. One study found the WHO technique more effective than the 3-step technique (P = .02), while another found no difference between these 2 techniques (P = .08). An adapted 3-step technique was more effective than the WHO technique in laboratory settings (P = .021), but not in clinical practice (P = .629). One study demonstrated that an adapted 6-step technique was more effective than the WHO technique (P = .001). Evidence was heterogeneous in application time, product, and volume. All studies were high risk of bias. CONCLUSIONS: Eight studies found that the WHO 6-step technique reduced microbial load on healthcare workers' hands; but the studies were heterogeneous and further research is required to identify the most effective, yet feasible technique.