Vaccination is a critical public health intervention in humanitarian and low- and middle-income country (LMIC) settings, where populations face heightened risks of vaccine-preventable diseases. Community Engagement (CE) offers a pathway to address challenges related to local ownership, trust, and acceptance, yet its effectiveness in these contexts remain underexplored. We conducted an umbrella scoping review of published reviews to synthesise evidence on the role of CE in vaccination delivery in humanitarian and LMIC contexts. Reviews were identified through searches of PubMed, Web of Science, Embase, and Google Scholar, screened in Covidence, and appraised using the Database of Abstracts of Reviews of Effects (DARE) criteria. Data were mapped against the International Federation of the Red Cross and Red Crescent Societies (IFRC) CE Impact Framework. Of 303 deduplicated studies, 39 met inclusion criteria. Most focused on routine childhood vaccines. CE activities were widespread, typically involving community participation, two-way communication, capacity strengthening, and feedback mechanisms. CE interventions were consistently associated with improved vaccine uptake, reduced hesitancy, and enhanced trust. Effective strategies included co-management of campaigns, engagement of religious and community leaders, culturally tailored communication, and school- or home-based delivery supported by trusted local figures. Multi-component interventions combining education, outreach, and digital tools were particularly effective. However, considerable variability existed in how CE was defined and operationalised across studies. CE should be recognised as a core pillar of vaccination strategy rather than an optional addition. It builds trust, fosters ownership, and addressed sociocultural barriers to access. Tailored, multi-component approaches leveraging trusted community figures are especially promising. Definitional ambiguity and inconsistent evaluation frameworks currently limit understanding of what works, for whom, and in what context. Future research should prioritise standardising CE definitions, developing context-sensitive theories of change, and strengthening methods for evaluating CE's contribution to vaccine coverage and equity.