Objective We aim to investigate the clinical value of prognostic nutritional index PNI in evaluating the prognosis of patients with metastatic pancreatic cancer. Method Clinical data and follow-up data of 83 patients with metastatic pancreatic cancer undergoing first-line chemotherapy from April 2017 to February 2022 in Zhongnan Hospital of Wuhan University were retrospectively collected and analyzed. PNI value was calculated and the optimal cut-off point of PNI was determined using the receiver operation characteristics ROC curve. Cox univariate and multivariate regression analysis and Kaplan-Meier curve were performed to evaluate the prognostic value of PNI for metastatic pancreatic cancer patients. Result According to the ROC curve analysis the optimal cut-off point of PNI was 43. 10. PNI was significantly correlated with objective response rate ORR progression free survival PFS and overall survival OS of patients with metastatic pancreatic cancer receiving first-line chemotherapy. The median PFS and median OS were 4. 61 95%CI = 3. 92-5. 30 and 9. 05 95%CI = 8. 20-9. 89 months respectively. The ORR in low PNI group and high PNI group was 5. 9% and 32. 7% respectively P<0. 05 . The median progression free survival time mPFS of patients in low PNI group and high PNI group were 2. 96 months 95%CI = 2. 53-3. 47 and 5. 67 months 95%CI = 4. 43-6. 21 respectively. There was a significant difference between the two groups P<0. 01 . Meanwhile the median overall survival time mOS of patients in the low PNI group and the high PNI group was 5. 92 months 95% CI = 5. 30 - 6. 55 and 11. 84 months 95% CI = 9. 10 - 14. 59 respectively. There was also a significant difference between the two groups P<0. 01 . Multivariate Cox regression analysis showed that PNI HR = 0. 123 95% CI = 0. 061- 0. 248 P< 0. 01 was an independent prognostic factor of OS in patients with metastatic pancreatic cancer. Conclusion PNI can be used as a prognostic factor for patients with metastatic pancreatic cancer.