Objectives: The neutrophil-to-lymphocyte ratio (NLR) is a prognostic marker in patients with cancer receiving immunotherapy. Recent studies have shown that a high NLR was associated with a poor response and decreased survival. However, there is no intervention to reverse abnormally high NLR and improve clinical outcomes. Astragalus polysaccharide injection (PG2) is an immunomodulatory therapy for cancer-related fatigue. This study aimed to examine whether PG2 might normalize the NLR and affect the overall survival of patients with lung cancer treated with immunotherapy. Materials and Methods: We retrospectively examined the medical records of patients with lung cancer treated with immune checkpoint inhibitors (ICIs) between October 1, 2015 and November 30, 2019. All patients received ICI combination chemotherapies, and some similarly received PG2 (Control vs PG2). The NLR was assessed before treatment and 6 weeks after ICI initiation, and the survival data was collected at least 4 years after treatment initiation for the first enrolled patient. Results: Fifty-three patients were included. Six weeks after ICI initiation, 91.3% of the patients in the PG2 group exhibited a predefined “Decrease or no change” in the NLR, which was 28% higher than that in the Control group (63.3%) ( P = .028). The NLR significantly decreased by 31.60% from baseline in the PG2 group ( P = .012), whereas it increased by 5.80% in the Control group ( P = .572). Six weeks after ICI treatment initiation, both groups had a median NLR of 3.73, and the overall survival was also similar (PG2 vs Control, 26.1 months vs 25.4 months, respectively); however, the PG2 group had a higher median baseline NLR than the Control group (PG2 vs Control, 4.51 vs 2.81, respectively). Conclusion: This study demonstrated that PG2 could normalize the NLR in patients with lung cancer receiving ICI combination treatments.