BACKGROUND: Infection with coronavirus SARS-CoV-2, causing COVID-19 disease, leads to inflammation and a prothrombotic state. OBJECTIVE: This rapid systematic review aims to synthesize evidence on thromboembolism incidence and outcomes with antithrombotic therapies in COVID-19. DATA SOURCES: We searched MEDLINE (Ovid), Cochrane Rapid Reviews, PROSPERO, and the WHO COVID-19 Database from January 1, 2003, to April 22, 2020, for studies meeting pre-specified inclusion criteria. STUDY SELECTION, DATA EXTRACTION, AND SYNTHESIS: One investigator identified articles for inclusion, abstracted data, and performed quality assessment, with second reviewer checking. RESULTS: Incidence of thromboembolism among hospitalized patients with COVID-19 ranged from 25 to 53% in 4 retrospective series. We identified 3 studies (1 retrospective cohort study, 1 prospective uncontrolled observational study, and 1 case series) examining outcomes among COVID-19 patients who received antithrombotic therapies. These studies all included different interventions (thromboprophylaxis with unfractionated heparin (UFH) or low molecular-weight heparin (LMWH); an intensive thromboprophylaxis protocol with LMWH, antithrombin, and clopidogrel; and salvage therapy with tissue plasminogen activator and heparin). These studies are overall poor quality due to methodological limitations including unclear patient selection protocols, lack of reporting or adjustment for patient baseline characteristics, inadequate duration of follow-up, and partial reporting of outcomes. CONCLUSIONS: New evidence on thromboembolism in COVID-19 does not warrant a change in current guidance on thromboprophylaxis among hospitalized patients. Prospective trials of antithrombotic treatment strategies among patients with COVID-19 are urgently needed.