Chimeric antigen receptor-T (CAR-T) cell therapy has emerged as an immunotherapy option for several hematological malignancies. Patients treated with CAR-T cell therapy are immunocompromised and prone to infections. However, limited data exist regarding prophylaxis and management strategies, which vary among institutions. We report a single-institution experience of adenovirus (AdV) infection treatment following CAR-T cell therapy. Case report. Academic referral center. A 67-year-old man with high-risk mantle cell lymphoma previously treated with chemoimmunotherapy and ibrutinib received brexucabtagene autoleucel for refractory disease. Treatment was complicated by grade 2 immune effector cell-associated neurotoxicity syndrome (ICANS), warranting corticosteroid treatment that was tapered over 4 weeks, and cytokine release syndrome (CRS), resolved with tocilizumab. The patient was admitted within 30 days post-CAR-T cell therapy with pancytopenia and bilateral pulmonary infiltrates. His only symptoms were fatigue and malaise. A respiratory viral panel was positive for AdV. Further infectious testing revealed AdV viremia at 128,000 copies/mL and viruria at 7.10E+07 copies/mL, as well as BK viremia at 5,200 copies/mL and viruria >62,800,000 copies/mL. The patient was initially treated with intravenous immune globulin and then started on intravenous cidofovir 1 mg/kg with pre- and post-hydration. Adenovirus and BK virus levels were monitored in blood and urine weekly. Cidofovir was continued until the plasma level of AdV was <400 copies/mL on two separate occasions. AdV viremia and viruria, BK virus viremia and viruria, symptoms. Viral levels of AdV steadily decreased over 3 weeks to <190 copies/mL in plasma and 5200 copies/mL in urine. No new symptoms other than intermittent hematuria were noted. BK virus plasma levels increased temporarily, but fluoroquinolones were not given due to allergy and scarce evidence of their efficacy. Immunosuppression in patients receiving CAR-T cell therapy is multifactorial. CRS and ICANS are common acute toxicities that frequently require treatment with immunosuppressive agents. Prolonged use of corticosteroids has been identified as a predictor of infection after CAR-T cell therapy. Clinical trials addressing appropriate infection prophylaxis and treatment in this population are needed.