While the advent of chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment of relapsed or refractory DLBCL, it is unclear how survival has changed at the population level following its approval. Herein, we performed a population-based cohort study using the SEER-17 database. The primary exposure was a period of diagnosis (2014-2017 vs. 2018-2021), and these periods were selected based on the first FDA-approval of CAR-T in 2017. Study outcomes were relative survival (RS), overall survival (OS), lymphoma-specific survival (LSS), and the cumulative incidence of death from lymphoma (CIF). A total of 51,584 patients with DLBCL were included in the study with 24,861 patients diagnosed in time period-1 (2014-2017) and 26,723 patients diagnosed in time period-2 (2018-2021). The median age at diagnosis was 68 years (interquartile range, 57-77) and most patients were White (n = 42,190, 82%) with advanced stage at diagnosis (n = 28,203, 55%). In unadjusted analysis, the 5-year RS (95% CI) increased from 64% from 2014 to 2017 to 66% from 2018 to 2021, while 5-year OS increased from 54 to 55%, and 5-year LSS increased from 64 to 66%. On competing risks analysis, the 5-year probability of death from lymphoma decreased from 34 to 31%. The improvements in survival were observed across age, disease stage, and racial groups, and remained significant when adjusting for age, sex, race, stage, B symptoms and documented receipt of chemotherapy in multivariable survival models (adjusted OS HR = 0.97, 95%CI = 0.94-1.00, p = 0.04; adjusted LSS HR = 0.93, 95%CI = 0.90-0.96, p < 0.001). We found improved survival for patients with DLBCL diagnosed between 2018 and 2021 when compared to those diagnosed between 2014 and 2017. These findings will serve as the benchmark for future studies evaluating the impact of CAR-T administered earlier in their disease course.