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ABSTRACT Background Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer cases and remains one of the leading causes of cancer-related mortality worldwide. Recent advances in immune checkpoint inhibitor therapy targeting PD-1/PD-L1 pathways have improved survival outcomes; however, only a subset of patients demonstrates durable clinical responses. Emerging evidence indicates that lung microbiome dysbiosis plays an important role in tumor progression, immune regulation, inflammatory pathways, and response to immunotherapy. Aim To assess the role of lung microbiome dysbiosis in NSCLC progression and its association with immunotherapy response among patients receiving immune checkpoint inhibitor therapy. Methods A prospective observational study was conducted among 100 diagnosed NSCLC patients receiving immunotherapy. Bronchoalveolar lavage (BAL) samples were collected for microbial profiling using 16S rRNA sequencing. Clinical characteristics, tumor stage, PD-L1 expression, inflammatory biomarkers, and immunotherapy response were assessed. Treatment response was evaluated according to RECIST 1.1 criteria. Data were analyzed using SPSS version 26.0. Results Among 100 NSCLC patients, lung microbiome dysbiosis was identified in 62% of cases. Advanced tumor stage (III-IV) was significantly associated with reduced microbial diversity (p<0.01). Patients with balanced lung microbiota showed a higher immunotherapy response rate (63.2%) compared with dysbiosis patients (32.3%). Increased abundance of Proteobacteria and reduced Firmicutes were associated with poor progression-free survival and resistance to immune checkpoint inhibitors. Conclusion Lung microbiome dysbiosis significantly influences NSCLC progression and immunotherapy response. Microbial profiling may serve as a potential biomarker for predicting treatment outcomes and developing microbiome-targeted therapeutic approaches.