ObjectiveThis living systematic review aims to evaluate the vertical transmission of SARS-CoV-2 through breast milk and breastfeeding in patients with COVID-19 providing a timely, rigorous and continuously updated summary of the evidence available on .Data sources We will conduct searches in the L·OVE (Living OVerview of Evidence) platform for COVID-19, a system that maps PICO questions to a repository maintained through regular searches in electronic databases, preprint servers, trial registries and other resources relevant to COVID-19. No date or language restrictions will be applied. In response to the COVID-19 emergency, L·OVE was adapted to expand the range of evidence it covers and customised to group all COVID-19 evidence in one place. The search will cover the period until the day before submission to a journal.Eligibility criteria for selecting studies and methodsWe adapted an already published common protocol for multiple parallel systematic reviews to the specificities of this question. We will include primary studies evaluating the role of breast milk and breastfeeding transmission. Randomised trials evaluating breast milk and breastfeeding in infections caused by other coronaviruses, such as MERS-CoV and SARS-CoV, and non-randomised studies in COVID-19 will be searched in case we find no direct evidence from randomised trials, or if the direct evidence provides low- or very low-certainty for critical outcomes.Two reviewers will independently screen each study for eligibility, extract data, and assess the risk of bias. We will pool the results using meta-analysis and will apply the GRADE system to assess the certainty of the evidence for each outcome. A living, web-based version of this review will be openly available during the COVID-19 pandemic. We will resubmit it every time the conclusions change or whenever there are substantial updates.