Objectives: The rapid evolution of the treatment landscape for non-small cell lung cancer (NSCLC) indicates a need to assess real-world treatment patterns in clinical practice in the US. This study aims to describe treatment patterns and patient characteristics taking into account new drug entities and newly emerging biomarkers for NSCLC. Methods: A descriptive cohort study was conducted using a specialized electronic health record data for NSCLC. Patients who initiated NSCLC treatment following diagnosis of advanced NSCLC (stage IIIB/IIIC/IV) from 01/01/2015-12/31/2021 were identified. Baseline characteristics and treatment patterns were described; continuous variables were described as mean and standard deviation (SD) and categorical variables as proportions. Results: Of 8,811 patients identified with advanced NSCLC, 67.9% had non-squamous cell carcinoma, 22.5% had squamous cell carcinoma, and 9.6% had an unknown histology. The majority of patients (78.7%) were treated at community hospitals, while 13.4% were treated at academic centers, and 7.9% had an unknown treatment setting. Most patients (59.0%) were aged 65 years or older, and 47.3% were female. There were 22 patients (0.2%) with documentation of NSCLC but no identified guideline-recommended line of therapy (LoT). Among all patient, 51.6% received a second line of therapy (LoT2), and 26.4% received third-line therapy (LoT3). For stage IIIB/IIIC patients, the five most common first-line therapies (LoT1), accounting for 83.2% of all LoT1, included traditional platinum-based chemotherapy or pembrolizumab. In stage IV patients, the five most common LoT1, comprising 64.4% of all LoT1, were pembrolizumab either as monotherapy or combined with other platinum-based chemotherapeutic agents. Conclusions: Traditional platinum-based chemotherapy was the most common LoT1 for stage IIIB/IIIC patients, while the extensive use of immunotherapy (IO) was found in stage IV patients and in later lines of treatment in stage IIIB/IIIC patients. The growing use of IO indicated that new evidence was rapidly adopted among NSCLC patients.