Importance The benefits of prophylactic antibiotics for hospitalized patients with severe alcohol-related hepatitis are unclear. Objective To determine the efficacy of amoxicillin-clavulanate, compared with placebo, on mortality in patients hospitalized with severe alcohol-related hepatitis and treated with prednisolone. Design, Setting, and Participants Multicenter, randomized, double-blind clinical trial among patients with biopsy-proven severe alcohol-related hepatitis (Maddrey function score ≥32 and Model for End-stage Liver Disease [MELD] score ≥21) from June 13, 2015, to May 24, 2019, in 25 centers in France and Belgium. All patients were followed up for 180 days. Final follow-up occurred on November 19, 2019. Intervention Patients were randomly assigned (1:1 allocation) to receive prednisolone combined with amoxicillin-clavulanate (n = 145) or prednisolone combined with placebo (n = 147). Main Outcome and Measures The primary outcome was all-cause mortality at 60 days. Secondary outcomes were all-cause mortality at 90 and 180 days; incidence of infection, incidence of hepatorenal syndrome, and proportion of participants with a MELD score less than 17 at 60 days; and proportion of patients with a Lille score less than 0.45 at 7 days. Results Among 292 randomized patients (mean age, 52.8 [SD, 9.2] years; 80 [27.4%] women) 284 (97%) were analyzed. There was no significant difference in 60-day mortality between participants randomized to amoxicillin-clavulanate and those randomized to placebo (17.3% in the amoxicillin-clavulanate group and 21.3% in the placebo group [ P = .33]; between-group difference, −4.7% [95% CI, −14.0% to 4.7%]; hazard ratio, 0.77 [95% CI, 0.45-1.31]). Infection rates at 60 days were significantly lower in the amoxicillin-clavulanate group (29.7% vs 41.5%; mean difference, −11.8% [95% CI, −23.0% to −0.7%]; subhazard ratio, 0.62; [95% CI, 0.41-0.91]; P = .02). There were no significant differences in any of the remaining 3 secondary outcomes. The most common serious adverse events were related to liver failure (25 in the amoxicillin-clavulanate group and 20 in the placebo group), infections (23 in the amoxicillin-clavulanate group and 46 in the placebo group), and gastrointestinal disorders (15 in the amoxicillin-clavulanate group and 21 in the placebo group). Conclusion and Relevance In patients hospitalized with severe alcohol-related hepatitis, amoxicillin-clavulanate combined with prednisolone did not improve 2-month survival compared with prednisolone alone. These results do not support prophylactic antibiotics to improve survival in patients hospitalized with severe alcohol-related hepatitis. Trial Registration ClinicalTrials.gov Identifier: NCT02281929