Background <p>Human behavioural research is often clouded with the risk that study results may be contaminated by the participant’s awareness that they are being observed. Direct observation by a person is associated with this phenomenon, but limited data exists evaluating this Hawthorne Effect when less invasive video recording devices are used. Here we present the first quantitative analysis to identify the extent to which this occurs, based on self-reported behavioural change when cameras are used.</p> Methods <p>Searches of MEDLINE, Embase, Emcare, PsycINFO, CINAHL, and Google Scholar were performed on 01/12/2022. No limitations were set. The primary outcome was the proportion of participants who changed their behaviour due to awareness of being recorded. Two blinded reviewers performed screening in accordance with PRISMA guidelines. <i>I</i>² statistic was used to assess for heterogeneity and a random effects model was subsequently applied for the meta-analysis.</p> Results <p>Preliminary searches identified 1728 publications. After screening, twenty-eight studies were included in the final analysis involving 2586 participants. Nine publications were suitable for quantitative analysis of the primary outcome. Pooled analysis using a random-effects model demonstrated the proportion of participants who reported behavioural change because of the camera was 15% (95% CI 0.08, 0.23) [<i>I</i>² = 96.16%]. </p> Conclusion <p>The presence of a video camera may cause behavioural change in a small proportion of study participants. Cameras may cause a much lower rate of reactivity compared to a direct human observer. The heterogeneity and high risk of bias of the publications highlight the need for further high-quality research into this subject area.</p> Systematic review registration <p>PROSPERO CRD42022370498</p>