Context: Unpaid carers are the backbone of long-term care (LTC) systems around the world. The COVID-19 pandemic has further increased the pressure many unpaid carers experience; however, their experience has been largely absent from public reporting. Objective: We aim to map the available evidence of the impacts of COVID-19 on unpaid carers of adults (>18 years) with LTC needs as well as of measures implemented to mitigate these effects and how well they have worked. Method: We conducted a rapid review of the academic and grey literature on unpaid carers of adults with LTC needs during the COVID-19 pandemic, covering the period until November 2020. Findings: We identified six key themes that highlight the impacts of COVID-19 on unpaid carers of people living in the community. These are: care commitment, concerns related to COVID-19, availability of formal and informal support, financial implications, carer health and well-being, and carers' adaptability. In addition, we captured aspects identified by unpaid carers supporting people in residential care settings under the theme 'carers of people in residential settings'. Finally, we reported evidence of measures implemented to mitigate the impacts on carers. This included the use of technology and the receipt of financial assistance and support for working carers. Limitations: The evidence reported in this review is based largely on cross-sectional data and some of the data reported relies on convenience samples. Implications: We highlight the financial and health impacts that many unpaid carers experience. Given the vital support carers provide to adults with LTC needs, policy makers should consider supporting unpaid carers to mitigate the negative impacts on their lives.