<h3>Objectives</h3> To quantitatively assess the early impact of the COVID-19 pandemic on in-person outpatient care utilisation worldwide, as well as across categories of services, types of care and medical specialties. <h3>Design</h3> Rapid review. <h3>Method</h3> A search of MEDLINE and Embase was conducted to identify studies published from 1 January 2020 to 12 February 2021, which quantitatively reported the impact of the COVID-19 pandemic on the amount of outpatient care services delivered (in-person visits, diagnostic/screening procedures and treatments). There was no restriction on the type of medical care (emergency/primary/specialty care) or target population (adult/paediatric). All articles presenting primary data from studies reporting on outpatient care utilisation were included. Studies describing conditions requiring hospitalisation or limited to telehealth services were excluded. <h3>Results</h3> A total of 517 articles reporting 1011 outpatient care utilisation measures in 49 countries worldwide were eligible for inclusion. Of those, 93% focused on the first semester of 2020 (January to June). The reported results showed an almost universal decline in in-person outpatient care utilisation, with a 56% overall median relative decrease. Heterogeneity across countries was high, with median decreases ranging from 10% to 91%. Diagnostic and screening procedures (−63%), as well as in-person visits (−56%), were more affected than treatments (−36%). Emergency care showed a smaller relative decline (−49%) than primary (−60%) and specialty care (−58%). <h3>Conclusions</h3> The provision of in-person outpatient care services has been strongly impacted by the COVID-19 pandemic, but heterogeneously across countries. The long-term population health consequences of the disruption of outpatient care service delivery remain currently unknown and need to be studied. <h3>PROSPERO registration number</h3> CRD42021237366.