Introduction Inhaled nebulised unfractionated heparin (UFH) has a strong scientific and biological rationale and warrants urgent investigation of its therapeutic potential for COVID-19. UFH has antiviral effects and prevents the SARS-CoV-2 virus’ entry into mammalian cells. In addition, UFH has significant anti-inflammatory and anti-coagulant properties, which limit progression of lung injury and vascular pulmonary thrombosis. Methods and intervention This meta-trial is a prospective collaborative individual patient data meta-analysis of randomised controlled trials and early phase studies. Individual studies are conducted in multiple countries. Adult patients admitted to the hospital with confirmed SARS-CoV-2 infection, who do not require immediate mechanical ventilation, are randomised to inhaled nebulised UFH or standard care. All studies collect a minimum core dataset. The primary outcome is intubation (or death, for patients who died before intubation) at day 28, assessed in a time-to-event analysis. The secondary outcomes are oxygenation, clinical worsening and mortality, assessed in time-to-event analyses. Individual studies may have specific outcome measures in addition to the core set. Ethics and dissemination: The meta-trial is registered at ClinicalTrials.gov, ID NCT04635241. Results of this study will be shared with the WHO, published in scientific journals and presented at scientific meetings.