Background and Objectives Several serum based‐markers and ratios have been investigated for their prognostic value in pancreatic ductal adenocarcinoma (PDAC). This cohort study aimed to combine these into a novel prognostic scoring system. Methods A retrospective cohort study was performed on 145 patients with unresectable histologically‐confirmed PDAC. Based on the existing literature the following markers were investigated: neutrophil‐lymphocyte ratio (NLR), neutrophil‐albumin ratio (NAR), platelet‐lymphocyte ratio (PLR), fibrinogen, and Ca19‐9. These values were dichotomized about their medians for Kaplan‐Meier and Cox regression analysis. Results Univariate Cox regression revealed statistically significant prognostic value for: NLR, NAR, PLR, fibrinogen, and Ca19‐9. When combining these using Cox regression analysis adjusting for other prognostic indicators, only NAR (hazard ratios HR = 3.174, P = 0.022) and Ca19‐9 (HR = 2.697, P = 0.031) were independent predictors of survival. Combining NAR and Ca19‐9 we split the cohort into three “NARCA” groups: NARCA0 = NAR ≤ 0.13 and Ca19‐9 ≤ 770, NARCA1 = either NAR > 0.13 or Ca19‐9 >770, NARCA2 = NAR > 0.13 and Ca19‐9 > 770. Median survival was 20.5, 9.7 and 4.1 months in NARCA0, 1, and 2 respectively ( P < 0.0005, log‐rank test). A separate validation cohort confirmed the prognostic significance of the score ( P = 0.048). Conclusions Combining NAR and Ca19‐9 into a prognostic score allows stratification of unresectable PDAC patients into groups with significantly different overall survival.