Purpose: Graded Prognostic Assessment (GPA) is a new prognostic index for patients with brain metastases. Brain metastasis is a common site of metastasis in lung cancers. Lung cancer-specific GPA scoring system is used. We aimed to assess the prognostic and predictive significance of Graded Prognostic Assessment (GPA) score in non small-cell lung cancer patients with brain metastasis. Materials and Methods: This study was designed as a hospital-based retrospective observational case-series study. A total of 95 patients with brain metastatic NSCLC patients who were followed in two different oncology centers in Turkey between 2015 and 2021 have been included into this study. They were divided into 3 groups according to their GPA scores. Results: The median age of the patients was 62 (range 44-89) years The patients were divided into 3 groups according to their GPA scores. 24 (25.2 %) patients had ‘’0-1’’ GPA score, 54 (56,8 %) patients had ‘’1,5-2’’ GPA score and 17 (18 %) patients had ‘’2,5-3’’ GPA score. The median follow-up time was 11 months and 89 (93.7%) patients died during follow-up. Overall survival (OS) was 8 months. Patients in the low (0-1) GPA scores had worst overall survival than those with higher GPA scores (4.7, 12.6 and 18.5 months respectively and p=0,001). Conclusion: In this study, we have shown that GPA score is useful in evaluating the prognosis of NSCLC patients with brain metastasis