High incidence of venous thromboembolic (VTE) events in coronavirus disease 2019 (COVID-19) patients has been reported despite pharmacologic thromboprophylaxis. We performed prospective bilateral lower extremity ultrasound evaluation of prolonged hospitalized COVID-19 ward patients from our institution without clinical suspicion of deep vein thrombosis (DVT).A total of 102 patient were included in the study. All patients were receiving pharmacologic thromboprophylaxis, the majority in intermediate or therapeutic doses. Asymptomatic DVT was detected in 26/102 (25.5%) patients: 22 had distal and four had proximal DVT, six had bilateral leg involvement. Pulmonary embolism was highly prevalent (17/70, 24.3%) but similarly grouped among patients with and without asymptomatic DVT. In total 37.2% of patients included in the study were recognized as having VTE.Asymptomatic DVT events were more common in intensive care unit (ICU) survivors (60% in postmechanically ventilated ICU survivors, 21.2% in ward patients, 22% in high-flow oxygen treated patients; P = 0.031), in patients with higher modified International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) VTE risk-score (median 3 vs. 2 points with and without DVT; P = 0.021) and higher body temperature on admission (median 38.7 °C vs. 37.7 °C with and without DVT; P = 0.001). No clear associations with Padua VTE risk score, demographic and other clinical characteristics, intensity of thromboprophylaxis, severity of other COVID-19 symptoms, degree of systemic inflammation or D‑dimers on admission were found (P > 0.05 for all analyses).Systematic ultrasound assessment in prolonged hospitalized severe COVID-19 patients prior to hospital discharge is needed, especially in ICU survivors, to timely recognize and appropriately treat patients with asymptomatic DVT.