Background/Aims: Predictors of short-term outcome of intravenous (IV) steroid therapy in acute severe ulcerative colitis (ASUC) have been well described, but the impact of cytomegalovirus (CMV) infection as a predictor of outcome remains debatable. We investigated the role of quantitative CMV polymerase chain reaction (PCR) as a predictor of short-term outcome in patients with ASUC. Methods: Consecutive patients with ASUC satisfying Truelove and Witts criteria hospitalized at All India Institute of Medical Sciences (AIIMS) from May 2016 to July 2019 were included; all received IV steroid. The primary outcome measure was steroid-failure defined as the need for rescue therapy (with ciclosporin or infliximab) or colectomy during admission. AIIMS’ index (ulcerative colitis index of severity > 6 at day 1+fecal calprotectin > 1,000 μg/g at day 3), with quantitative CMV PCR on biopsy samples obtained at initial sigmoidoscopy were correlated with the primary outcome. Results: Thirty of 76 patients (39%) failed IV corticosteroids and 12 (16%) underwent surgery. Patients with steroid failure had a significantly higher mucosal CMV DNA than responders (3,454 copies/mg [0–2,700,000] vs. 116 copies/mg [0–27,220]; P< 0.01). On multivariable analysis, mucosal CMV DNA load > 2,000 copies/mg (odds ratio [OR], 10.2; 95% confidence interval [CI], 2.6–39.7; P< 0.01) and AIIMS’ index (OR, 39.8; 95% CI, 4.4–364.4; P< 0.01) were independent predictors of steroid-failure and need for colectomy. The combination correctly predicted outcomes in 84% of patients with ASUC. Conclusions High mucosal CMV DNA ( > 2,000 copies/mg) independently predicts failure of IV corticosteroids and short-term risk of colectomy and it has an additional value to the established markers of disease severity in patients with ASUC.