Abstract Purpose To assess risk factors for arterial and venous thromboses (AVT) in patients hospitalized in general wards for COVID-19 pneumonia and requiring oxygen therapy. Methods Our study was based on three randomized studies conducted as part of the CORIMUNO-19 platform in France between 27 March and 26 April 2020. Adult inpatients with COVID-19 pneumonia requiring at least 3 l/min of oxygen but not ventilation were randomized to receive standard care alone or standard care plus biologics. Patients were followed up for 3 months, and adverse events were documented. Risk factor for AVT and bleeding was identified by analyzing clinical, laboratory, and treatment data at baseline among the 315 patients with complete datasets. A Fine and Gray model was used to take account of competing events. Results During the 3-month follow-up period, 39 AVT occurred in 38 (10%) of the 388 patients: 26 deep vein thromboses and/or pulmonary embolisms in 25 (6%) patients, and 14 arterial thrombotic events in 13 (3%) patients. A history of diabetes at inclusion [sHR (95% CI) = 2.65 (1.19–5.91), P = .017] and the C-reactive protein (CRP) level (sHR = 1 [1–1.01], P = .049) were significantly associated with an elevated risk of thrombosis. Obesity was not associated with a higher risk of thrombosis (sHR = 1.01 [0.4–2.57], P = .98). The CRP level and diabetes were not risk factors for hemorrhage. Conclusion Among patients hospitalized in general wards for COVID-19 pneumonia during the first wave of the epidemic, diabetes (but not obesity) and a high CRP level were risk factors for AVT. The use of higher doses of anticoagulant in these high-risk patients could be considered.