BACKGROUND AND OBJECTIVE: Sintilimab is a selective PD-1 inhibitor with efficacy in advanced or metastatic nonsquamous non-small-cell lung cancer (NSCLC) patients. This study evaluated the cost-effectiveness of sintilimab + chemotherapy versus camrelizumab + chemotherapy as the first-line treatment for locally advanced or metastatic nonsquamous NSCLC in Chinese patients. In addition, this study aimed to reveal the impact of the reference treatment choice on the incremental cost-effectiveness ratio (ICER) results. METHODS: A partitioned survival model (PSM) with three health states was constructed in a 3-week cycle with a lifetime horizon from the Chinese healthcare system perspective. Anchored matching adjusted indirect comparison was used for survival analyses based on individual patient data from Orient-11. Sintilimab + chemotherapy was chosen as the reference treatments in scenarios 1 and 2, while the camrelizumab + chemotherapy was chosen as the reference treatments in scenario 3. The utility values of different health states were derived from the patient-level European Organization for Research and Treatment Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) scores by mapping to the EQ-5D-5L, and QALYs were calculated as the health outcomes. One-way deterministic sensitivity analysis (DSA) and probability sensitivity analysis (PSA) were performed to explore model uncertainty. RESULTS: Compared to camrelizumab + chemotherapy, sintilimab + chemotherapy was associated with higher effectiveness (incremental QALYs ranged from 0.13-0.62) and lower total costs (incremental costs ranged from $1,099-$5,201), resulting in an ICER ranging from $6,440-$8,454/QALY. CONCLUSIONS: Sintilimab + chemotherapy is a cost-effective option compared with camrelizumab + chemotherapy as the first-line treatment for locally advanced or metastatic nonsquamous NSCLC in China.