Abstract Background Limited data are available regarding antiviral therapy efficacy in most severe patients under mechanical ventilation for Covid-19-related acute respiratory distress syndrome (ARDS). Methods Comparison of antiviral strategies (none, hydroxychloroquine (OHQ), lopinavir/ritonavir (L/R), others (combination or remdesivir) in an observational multicentre cohort of patients with moderate-to-severe Covid-19 ARDS. The primary endpoint was the number of day 28 ventilator-free days (VFD). Patients who died before d28 were considered as having 0 VFD. The variable was dichotomized into “patients still ventilated or dead at day 28” versus “patients weaned and alive at day 28”. Results We analyzed 415 patients (85 treated with standard of care (SOC), 57 with L/R, 220 with OHQ, and 53 others). The median number of d28-VFD was 0 (IQR 0–13) and differed between groups ( P = 0.03), SOC patients having the highest d28-VFD. After adjustment for age, sex, Charlson Comorbidity Index, PaO 2 /FiO 2 ratio and plateau pressure and accounting for center effect with a generalized linear mixed model, none of the antiviral strategies increased the chance of being alive and weaned from MV at day 28 compared to the SOC strategy (OR 0.48 CI95% (0.18–1.25); OR 0.96 (0.47–2.02) and OR 1.43 (0.53–4.04) for L/R, OHQ and other treatments, respectively). Acute kidney injury during ICU stay was frequent (55%); its incidence was higher in patients receiving lopinavir (66 vs 53%, P = 0.03). After adjustment for age, sex, BMI, chronic hypertension and chronic renal disease, the use of L/R was associated with an increased risk of renal replacement therapy (RRT). (OR 2.52 CI95% 1.16–5.59). Conclusion In this multicentre observational study of moderate-to-severe Covid-19 ARDS patients, we did not observe any benefit among patients treated with OHQ or L/R compared with SOC. The use of L/R treatment was associated with an increased need for RRT. Take home message Neither hydroxychloroquine nor lopinavir/ritonavir as COVID-19 antiviral ...