BackgroundThe rarity yet high malignancy of gallbladder adenocarcinoma (GBA) endows it with a distinctive nature. Radical resection remains the foremost therapeutic approach for GBA, while the impact of early recurrence and metastasis on patient prognosis necessitates the utilization of adjuvant chemotherapy (AC). Despite numerous previous studies on this topic, a consensus regarding the authentic efficacy of AC has yet to be reached. MethodsWe conducted an updated retrospective cohort analysis utilizing data from the Surveillance, Epidemiology, and End Results (SEER) database spanning from 2010 to 2020 to explore the association between AC and survival outcomes in patients with resected GBA. ResultsOur study included 2782 patients from the SEER database, with further evaluation of 843 patients in each cohort following meticulous execution of a 1:1 propensity score matching. Remarkably, the AC cohort exhibited a significant survival advantage when juxtaposed against the non-AC cohort. Multivariable Cox regression analysis identified age at diagnosis, year at diagnosis, grade, AJCC T stage, AJCC N stage as well as AC as independent prognostic factors. Furthermore, our findings unveiled that poor/undifferentiated tumor histology, pathological T2 or higher category and pathological N1 category were significantly associated with improved survival when treated with AC while simultaneously observing improved survival across all age categories. ConclusionThese results provide additional evidence supporting the survival benefits of AC and offer guidance for personalized therapy in patients with resected GBA.