Clinical trials indicated that PD-1/PD-L1 inhibitors significantly improve the survival rate of patients with advanced non-small cell lung cancer (NSCLC) and induce immune-related adverse events (irAEs). Thus, the molecular and immune characteristics during PD-1/PD-L1 inhibitor therapy are worth investigating further. We report the case of a 62-year-old male patient diagnosed with stage IIIA squamous cell lung carcinoma (SQCC) who responded to neoadjuvant and adjuvant nivolumab combined chemotherapy but died from anastomosis leakage or/and irAEs. In the pretreatment tumor biopsy, PD-L1 expression was negative and a few T cells, NK cells, and macrophages had infiltrated the tumor. Wild-type EGFR/STK11, mutant TP53, microsatellite stability, and low tumor mutational burden were also found at baseline. After neoadjuvant immunochemotherapy, the tumor was significantly reduced, PD-L1 expression levels were increased by 50%, and more CD8+ and CD8+ PD-1+ T cells had infiltrated the resected tumor tissue. Immune-related lung injury occurred during adjuvant immunochemotherapy, and serum levels of C-reactive protein, IL-13, IL-4, eotaxin, VEGF-A, IL-8, and IFN-gamma were increased. This case demonstrates a squamous cell lung carcinoma patient who responded to neoadjuvant immunochemotherapy that reshaped the tumor immune environment from "cold" to "hot." Unfortunately, the patient eventually died from anastomosis leakage or/and irAEs during adjuvant immunochemotherapy.