Background: Ongoing innovation in mantle cell lymphoma (MCL) has yielded new treatment options for patients in recent years. Yet, real-world treatment patterns, health care utilization, and costs associated with MCL are not well studied. Because MCL predominantly affects older adults (median age at diagnosis at 70), this study aimed to examine treatment patterns, health resource use (HRU), costs, and survival in a national sample of elderly Medicare beneficiaries newly diagnosed with MCL. Methods: This retrospective administrative claims study used national Medicare claims data from 2009 to 2019, the most recently available data at the time of the analysis. The sample included older patients (≥66 years) newly diagnosed with MCL between 01/01/2010 to 12/31/2018 (index date = first MCL diagnosis date). Patients were required to have continuous Medicare fee-for-service Part A, B, and D coverage in the 12 months pre-index and a minimum of 12 months post-index, no diagnoses for MCL and absence of any anticancer treatment in the 12 months pre-index (i.e. to identify new MCL cases), and evidence of at least one MCL-indicated treatment over follow-up after initial MCL diagnosis. Outcomes included treatment patterns, all-cause and MCL-related HRU and costs, and overall survival in the frontline and relapsed/refractory settings. Results: We identified 3664 patients receiving MCL treatment in the frontline setting (mean age 75.9, 28.2% age >80 years; 66.1% male; 92.8% White). Over half of frontline patients (50.1%) initiated bendamustine-rituximab, 16.1% received CHOP-based therapy, and 9.3% received rituximab monotherapy. During a median follow up of 2.8 years, approximately 40% of patients went on to receive at least second-line treatment [2L+]; nearly 18% and 8% received at least third-line treatment [3L+] and fourth-line treatment [4L+], respectively. Few patients received a stem cell transplant (5.6%). In the relapsed/refractory setting, use of non-cytotoxic therapies increased, most commonly BTKi-based (39.4% [2L+], 31.9% [3L+], 35.6% [4L+]), bortezomib-based (10.9% [2L+], 16.2% [3L+], 12.0% [4L+]), or lenalidomide-based regimens (4.4% [2L+], 11.6% [3L+], 15.8% [4L+]). The median time to next treatment from the end of the previous line of treatment ranged from about 1 month to 3.5 months (106.5 days from 1L to 2L, 28.0 days from 2L to 3L, and 40.5 days from 3L to 4L). Across all lines of therapy, HRU was substantial in the 12 months after initiating a given line of treatment. For instance, over half of patients (52%) had a hospitalization due to any cause, most of which were MCL-related. Hospice use increased in each line of therapy (11% [1L+], 22% [2L+], 34% [3L+], 41% [4L+]). Across all lines of therapy, over 80% of costs were attributable to MCL. Mean MCL-related total healthcare costs in the 12 months after initiation of treatment were $114,369 (1L+), $113,768 (2L+), $113,116 (3L+), and $115,883 (4L+). Mean MCL-related prescription drug costs were $73,398 in the 1L+ setting; the vast majority (87%, $63,749) were for physician-administered Part B drugs rather than Part D costs (13%, $9,650). Part D drugs costs made up a much larger share (55-65%) of MCL-related prescription drug costs in the relapsed/refractory setting ($41,925 [2L+], $41,003 [3L+], $40,381 [4L+]). Excluding patients who died within 12-months of treatment initiation, MCL-related total costs were higher for later lines of treatment ($127,820 [2L+], $137,761 [3L+], $155,865 [4L+]). Median OS from initial MCL diagnosis or 1L treatment initiation was 57.6 months and 53.5 months, respectively. Median OS was 22.0 months, 11.8 months, and 7.8 months from the initiation of 2L, 3L, and 4L treatment, respectively. The 1-year and 3-year survival rate was 81.3% and 60.6% from 1L treatment initiation and 63.8% and 38.0% from 2L treatment initiation, respectively. Conclusions: Our study of U.S. Medicare beneficiaries diagnosed with MCL found high rates of hospitalization and hospice care, substantial healthcare costs, and poor OS in later lines of therapy. As data on novel therapies accumulate, future studies should examine how they have alleviated unmet needs in elderly patients with MCL to support prioritization of access to newer treatments with better efficacy, durability, and tolerability in this population.