Objectives: With a lack of existing comprehensive reviews, the aim of this mixed-method systematic review was to synthesise the evidence on the early impacts of the pandemic on unpaid dementia carers across the globe. Methods: This review was registered on PROSPERO [CDR42021248050]. PubMed, CINAHL, Embase, Scopus and Web of Science were searched from 2020 to July 2021. Studies were included if they reported on the different impacts of the pandemic on unpaid dementia carers aged 18+, with papers published in English, German, Polish, or Spanish. A number of research team members were involved in the selection of studies following PRISMA guidance. Results: Thirty-six studies (43 papers) from 18 countries reported on the early impact of the pandemic on unpaid dementia carers. Impacts were noted on accessing care and support; carer burden; and well-being. Studies found that carers had limited access to care and support services, increased workload, enhanced feelings of social isolation, and reduced wellbeing. Specifically, reductions in access to care and support increased carer’s unpaid caring tasks, removing any opportunities for temporary respite, and thus further increasing carer burden and reducing mental well-being in many. Conclusions: The needs of unpaid dementia carers appear to have increased during the pandemic, without adequate support provided. Policy initiatives need to enable better mental health support and formal care provision for unpaid carers and their relatives with dementia, whilst future research needs to explore the long-term implications of carer needs in light of care home restrictions and care delivery.