This study estimated the total costs associated with tisagenlecleucel treatment in adult patients with relapsed/refractory (r/r) diffuse large B-cell lymphoma (DLBCL) based on the JULIET trial from a United States hospital's perspective. An economic model was developed to assess the total costs associated with tisagenlecleucel treatment (from leukapheresis to two months post-infusion) in adults (aged ≥18 years) with r/r DLBCL using a fee-for-service approach. Costs were considered during the pre-treatment, tisagenlecleucel infusion, and follow-up periods, and were estimated based on the health resource utilization and safety data from the JULIET trial. Cost components included leukapheresis, lymphodepleting chemotherapy, tisagenlecleucel infusion/administration, inpatient and intensive care unit (ICU) admission, medical professional visits, lab tests/procedures, and management of adverse events (AEs). The base-case model estimated the total costs using observed hospitalization, ICU, and AE data from JULIET, while scenario analyses varied key assumptions related to AEs and hospitalization. The estimated overall cost associated with tisagenlecleucel treatment from leukapheresis to two months post-infusion was $437,927/patient, of which $64,784 (14.8%) was additional to tisagenlecleucel's list price ($373,000) and the associated administration cost ($143). The top three key drivers of the additional cost were AE management ($30,594; 47.2%), inpatient/ICU not attributed to AEs ($24,285; 37.5%), and lab tests/procedures ($5,443; 8.4%). In the scenario analyses, total costs ranged from $382,702 (no AEs, no hospitalization) to $469,006 (cytokine release syndrome and B-cell aplasia, hospitalization).: This analysis was limited to two months of follow-up after tisagenlecleucel infusion, which cannot capture long-term safety outcomes associated with the treatment and may underestimate AE costs. The total cost of tisagenlecleucel administration from leukapheresis to two months was estimated at $437,927. In addition to tisagenlecleucel's price, the main drivers were AE management costs and inpatient/ICU costs. Future studies based on real-world, long-term use of tisagenlecleucel are warranted.