Background: IL6 and YKL-40 (also known as chitinase 3-like 1 protein, CHI3L1) are produced by pancreatic cancer cells and macrophages and activate inflammation. C-reactive protein (CRP) is synthesized mainly in hepatic cells and primarily stimulated by IL6. The aim of this study was to determine the prognostic value of combined detection of serum IL6, YKL-40, and CRP in patients with pancreatic cancer receiving palliative chemotherapy. Methods: In all, 592 patients with unresectable pancreatic cancer from five hospitals in Denmark were included in the BIOPAC biomarker study between 2008 and 2017. Pretreatment and longitudinal serum values of IL6 and YKL-40 were determined. Baseline CRP and CA19-9 values were available for the whole cohort. Patients were dichotomized as low versus high using cutoffs for IL6 of >4.92 pg/mL, YKL-40 of >95% age-corrected percentile, and CRP of >10 mg/L. The main outcome was overall survival. Results: Combined elevations of serum IL6, YKL-40, and CRP were associated with worse survival in contrast to an isolated high concentration of a single marker. Serum IL6, YKL-40, and CRP were higher in patients with advanced stage disease and in patients with poor performance status. Higher IL6 and YKL-40 levels at the time of tumor progression and serum IL6 measured over time were associated with shorter overall survival. Conclusions: Combined high baseline serum levels of IL6, YKL-40, and CRP are associated with poor survival. Impact: Assessment of systemic inflammation via measurements of IL6, YKL-40, and CRP may be important for pancreatic cancer prognostication.