Clinical studies aimed at identifying effective and simple prognostic markers for gastric cancer are still being carried out. Inflammatory prognostic index (IPI) is being recognized as a promising prognostic marker in patients with Non-Small Cell Lung Cancer. To evaluate the prognostic utility of IPI in stage 4 gastric cancer. A total of 152 patients with stage 4 gastric cancer, whose laboratory parameters, progression-free survival (PFS) and overall survival (OS) data could be accessed, were evaluated. Kaplan Meier analysis was used for survival analyses. Hazard ratios were expressed with 95% CI values. All methods were performed in accordance with the relevant guidelines and regulations. Study was approved by the Manisa Celal Bayar University’s Non-Invasive Clinical Research Ethics Committee (approval No. E-85252386-050.04.04-49119, date: 22.03.2021). We confirm that all methods were performed in accordance with relevant named guidelines and regulations. Median age at diagnosis was 63 years (range: 32–88). The number of patients who received first-line chemotherapy was 129 (84.9%). Median PFS with first-line treatment was 5.3 months, while it was 3.3 months with second-line treatment. Median OS was 9.4 months. Median IPI score was 22.2. We evaluated IPI score for its value in detecting survival status with ROC analysis and identified an IPI cut-off score of 14.6. Low IPI score was significantly associated with longer PFS and OS compared to high IPI (PFS in high vs. low IPI, 3.6 vs. 7 months;p< 0.001) (OS in high vs. low IPI, 6.6 vs. 14.2 months;p< 0.001). IPI score can be an independent prognostic index that is inexpensive, easy to access and evaluate for patients with metastatic gastric cancer, and may be useful in predicting survival in daily practice.