Abstract Background Opportunities for social connection between generations in the UK have diminished over the last few decades because of changes in the way that we live and work. The decline in communal spaces such as libraries, youth clubs and community centres mean that there are fewer opportunities to meet and mix socially with other generations outside our own families. Increased working hours, improved technology, changes in family patterns, relationship breakdowns within families and migration are also believed to be contributory factors to generation segregation. There are many potential economic, social and political impacts of generations living separate and parallel lives, for example, higher health and social care costs, an undermining of trust between generations reduced social capital, a reliance on the media to form understanding of others’ viewpoints and higher levels of anxiety and loneliness. Intergenerational programmes and activities can take many forms and are delivered in many settings. Evidence suggests that intergenerational activity can have a positive impact on participants, for example, in reducing loneliness and exclusion for both older people and children and young people, improving mental health, increasing mutual understanding and addressing important issues such as ageism, housing and care. There are currently no other EGMs that exist that address this type of intervention; however, it would complement existing EGMs addressing child welfare. Objectives To identify, appraise and bring together the evidence on the use of intergenerational practice, to answer the following specific research questions: What is the volume, nature and diversity of research on, and evaluation of, intergenerational practice and learning? What approaches have been used to deliver intergenerational activities and programmes that may be relevant to providing such services during and in the subsequent recovery from the COVID‐19 pandemic? What promising intergenerational activities and programmes have been developed and are being used but have not yet been subject to formal evaluation? Search Methods We searched MEDLINE (via OvidSp), EMBASE (via OvidSp), PsycINFO (via OvidSp), CINAHL (via EBSCOHost), Social Policy and Practice (via OvidSp), Health Management Information Consortium (via OvidSp), Ageline (via EBSCOhost), ASSIA (via ProQuest), Social Science Citations Index (via Web of Science), ERIC (via EBSCOhost), Community Care Inform Children, Research in Practice for Children, ChildData (via Social Policy and Practice), the Campbell Library, the Cochrane Database of Systematic Reviews and the CENTRAL database between 22 and 30 July 2021. We searched for additional grey literature via the Conference Proceedings Citation Index (via Web of Science) and ProQuest Dissertation & Theses Global and via relevant organisation websites, for example, Age UK, Age International, the Centre for Ageing Better, Barnado's, Children's Commission, UNICEF, Generations Working Together, the Intergenerational Foundation, Linking Generations and The Beth Johnson Foundation) and the Ottawa initiative called Older Adults and Students for Intergenerational support. Selection Criteria Any intervention that brings older and younger people together with the purpose of interacting to achieve positive health and/or social and/or educational outcomes from any study design including systematic reviews, randomised controlled studies, observational studies, surveys and qualitative studies are included. The titles and abstracts, and later full texts, of records identified by the search methods were screened against inclusion criteria by two independent reviewers. Data Collection and Analysis Data extraction was undertaken by one reviewer and checked by a second with any inconsistencies identified and resolved through discussion. The data extraction tool was developed on EPPI reviewer and was modified and tested through stakeholder and advisor consultation, and piloting of the process. The tool was informed by the research question and the structure of the map. We did not undertake quality appraisal of the included studies. Main Results Our searches identified 12,056 references, after screening 500 research articles were included in the evidence gap map conducted across 27 countries. We identified 26 systematic reviews, 236 quantitative comparative studies (of which 38 were randomised controlled trials), 227 were qualitative studies (or had a qualitative element), 105 were observational studies (or had elements of observational methods) and 82 used a mixed methods approach. The outcomes reported in the research cover mental health (n = 73), physical health (n = 62), attainment and knowledge (n = 165), agency (n = 174), mental wellbeing (n = 224), loneliness and social isolation (n = 54), attitudes towards the other generation (n = 283), intergenerational interactions (n = 196), peer interactions (n = 30) and health promotion (n = 23) and including mutual outcomes such as the impact on community (n = 37) and perceptions on the sense of community (n = 43). Gaps in the evidence that were identified include: research that reports on mutual, societal and community outcomes of intergenerational interventions; more research on interventions classified as levels 1–4 and level 7 on the Intergenerational Engagement Scale, mental health, loneliness, social isolation, peer interactions, physical health and health promotion outcomes in children and young people; health promotion in older people; outcomes centred on care giver wellbeing, mental health and attitudes; economic outcomes; process outcomes and adverse or unexpected outcomes. Authors’ Conclusions Whilst a substantional amount of research on intergenerational interventions has been identified in this EGM, as well as the gaps identified above, there is a need to explore promising interventions not yet formally evaluated. Research on this topic is gradually increasing, and systematic reviews will be important to determine how and why interventions are or are not beneficial. However, the primary research needs to build more cohesively so that the findings can be comparable and avoid research waste. The EGM presented here will nevertheless be a useful resource for decision‐makers allowing them to explore the evidence with regard to the different interventions that may be relevant to their population needs and the settings or resources available to them.