<p>Universal mental health screening (UMHS) in schools has strong potential to support early identification of mental health problems in young people. Despite likely benefits implementation remains low, with the lack of evidence regarding acceptability of screening to key stakeholders a contributing factor. We systematically assessed the current evidence base for acceptability of UMHS in schools and its status within key stakeholder groups. MEDLINE, Embase, PyschINFO, Education Research Complete, ASSIA, and Web of Knowledge were searched for relevant articles. All study types collecting acceptability UMHS in schools were included spanning three key stakeholder groups as informants. Articles were assessed for quality using the Mixed Methods Appraisal Tool with outcome data assessed via narrative synthesis and standardised scoring employing the Theoretical Framework for Acceptability Questionnaire. Our review identified 28 studies representing 11,854 informants providing acceptability data on universal mental health screening in schools. Quality of studies varied and designs heterogenous, with wide variation in how acceptability was defined and measured resulting in a weak evidence base. Only 8 studies employed validated acceptability measures. We found some evidence of moderate to high acceptability for all stakeholders, especially school staff, however overall data on acceptability is limited. Of particular concern is a paucity of acceptability data for young people, especially primary school pupils. Schools should consider assessing pupil perspectives on acceptability outside of screening to further understand drivers of non-participation and mitigate any risks of exacerbating health inequalities.</p>