BACKGROUND: We aimed to contribute to the ongoing discussion regarding adjuvant treatment strategies following neoadjuvant chemoimmunotherapy (NCIT) and adjuvant immunotherapy (AIT) after upfront surgery (US) in patients with resectable non-small cell lung cancer (NSCLC). METHODS: 317 patients were retrospectively included from 2019 to 2024. 285 received NCIT, while 32 received AIT after US. The patients were categorized into no-treatment (n = 46), chemotherapy (ChT) (n = 38), immunotherapy (IT) (n = 33), chemoimmunotherapy (ChIT) (n = 168), and US + AIT groups. Event-free survival (EFS) and overall survival (OS) were assessed using the Kaplan-Meier method. Groups were compared using the log-rank test. Subgroup analyses include stage, pathological response, and programmed cell death ligand 1 (PD-L1) expression level. Propensity score matching (PSM) was used to balance baseline differences. RESULTS: The median follow-up was 30.7 months. Before and after PSM, the IT and ChIT groups demonstrated better EFS compared with the no-treatment group. After PSM, EFS was significantly prolonged with IT and ChIT in patients who did not achieve a pathological complete response (pCR). In patients who achieved pCR, no benefit in EFS or OS was observed. Among patients with a PD-L1 expression of ≥ 1%, EFS was significantly improved with IT and ChIT compared with the no-treatment and US + AIT groups respectively. Similar EFS benefits for IT and ChIT were observed across stage IB-IIB and IIIA-IIIB subgroups. CONCLUSION: Adjuvant IT or ChIT potentialy benefit patients with resectable NSCLC receiving NCIT, particularly those without pCR and with positive PD-L1 expression.