BACKGROUND: Chemotherapy-induced myelosuppression (CIM) is the most common adverse event associated with chemotherapy. The recently approved novel pharmacotherapy trilaciclib demonstrates potential to provide multilineage protection against CIM. This study aimed to evaluate the cost-effectiveness of trilaciclib among patients with extensive-stage small cell lung cancer (ES-SCLC) in China. RESEARCH DESIGN AND METHODS: A short-term Markov model and long-term partitioned survival model were developed to simulate disease progression during and after chemotherapy over a lifetime horizon. Clinical, cost, and utility parameters were obtained from three pivotal clinical trials of trilaciclib, published literature, and expert opinion. Total cost, quality-adjusted life years (QALYs), and incremental cost-effectiveness ratios (ICERs) were calculated. Scenario analyses and sensitivity analyses assessed model robustness. RESULTS: The lifetime incremental cost per patient for trilaciclib was CN¥22,828 (US,210), with an incremental QALY of 0.093, yielding an ICER of CN¥245,841 (US4,565) per QALY gained. This ICER falls below China's willingness-to-pay threshold of three times per-capita GDP (CN¥268,074, US7,691). Extensive sensitivity analyses confirmed the robustness of the base-case findings. CONCLUSIONS: Trilaciclib represents a cost-effective option for reducing the incidence of CIM in ES-SCLC patients. These results support reimbursement decisions and pricing strategies for trilaciclib in China.