Background Immunotherapy has become a standard treatment for lung cancer; however, the high cost makes it necessary to assess health outcomes. Objective The aim of this study was to evaluate the effectiveness, safety and economic cost of nivolumab in real-world clinical practice. Setting Fifteen regional and academic hospitals from Spain participated in this study. Methods This study was a retrospective, multicentre and observational study involving patients who experienced progression after first-line therapy for non-small-cell lung cancer and were treated with nivolumab between January 2016 and July 2017. Effectiveness and safety were evaluated by the oncologist, and the data from the electronic clinical records of the patients were collected by the research team. Economic cost was calculated using the cost of acquiring nivolumab for the public health system. Main outcome measures Effectiveness variables were overall survival (OS) and progression-free survival (PFS). The safety variable was the incidence of adverse events (AEs), and the cost per life-year gained (LYG) was the economic variable. Results A total of 221 patients were enrolled (83.7% men). The mean age was 64.5 years, and 84.6% of the patients had an Eastern Cooperative Oncology Group (ECOG) performance-status score of 0-1. Squamous tumours accounted for 59.7% of the total, and 78.7% of the patients presented a time since platinum therapy (TPT) > 6 months. The mean nivolumab dose was 216 mg (SD 211), and the treatment duration was 7.0 months (95% CI 5.8-8.1). The median PFS was 5.3 months (95% CI 3.2-7.3), and OS was 9.7 months (95% CI 7.6-11.8). The median PFS and OS values were statistically significantly superior for patients with an ECOG score of 0-1 and for patients with a TPT > 6 months. The median OS was also statistically significantly superior for patients with non-squamous histology. Regarding safety, 71% of the patients presented AEs of any grade, and in 18.6%, the nivolumab treatment had to be delayed or discontinued. The cost of nivolumab per patient was €19,910.00 (SD 19,369), and the cost per LYG was €110,026.00 (€77,557.00-€231,171.00). Conclusions This study confirms that the efficacy and safety of nivolumab treatment in a real population are comparable to the results obtained in clinical trials. A greater clinical benefit of nivolumab therapy was observed in patients with an ECOG score of 0-1, a TPT > 6 months or non-squamous histology. Despite the benefit observed, the cost per LYG is above the threshold of efficiency established by public health institutes.