Background: IL-6 and YKL-40, markers of inflammation and cancer growth, are high in serum in patients with colorectal cancer (CRC) and associated with shorter overall survival (OS). We hypothesized that preoperative serum IL-6, YKL-40 and CEA are associated with disease free survival (DFS) and OS in patients with metastatic (mCRC) treated with liver resection. Methods: 457 patients (male/female: 267 (58%)/190 (42%), median age 65 [IQR: 58-71]) diagnosed with mCRC who underwent liver resection were included between March 1998 and February 2013. Preoperative serum samples were collected and stored at -80°C until analysis. Serum IL-6 (R&D Systems, UK) and YKL-40 (Quidel, USA) were determined by ELISA. For DFS and OS we estimated crude and adjusted hazard ratios (HR) and corresponding 95% confidence intervals (CIs) with Cox regression for each biomarker separately. The biomarkers were included as log₂-transformed continuous variables and adjustment included mutual adjustment between the biomarkers in addition to adjusting for sex and age. Results: The median (IQR) preoperative biomarker levels were: IL-6 (3.5 pg/ml, 2.1-6.1), YKL-40 (75 ng/ml, 48-127) and CEA (5.2 kU/L, 2.6-18.8). Univariate analysis showed that high serum IL-6 and YKL-40 were associated with shorter DFS (IL-6: HR = 1.18, 1.06-1.31, p < 0.01; YKL-40: HR = 1.19, 1.08-1.32, p < 0.01). Serum CEA was not (p = 0.80). Multivariate analysis (all biomarkers) showed that high IL-6 was associated with shorter DFS (HR = 1.15, 1.02-1.29, p = 0.02), whereas YKL-40 (p = 0.08) and CEA (p = 0.51) were not. Univariate analysis showed that high preoperative serum IL-6 and YKL-40 were associated with shorter OS (IL-6: HR = 1.16, 1.03-1.29, p = 0.01; YKL-40: HR = 1.27, 1.14-1.42, p < 0.01). Serum CEA was not associated with OS (p = 0.16). Multivariate analysis (all biomarkers) showed that high YKL-40 was associated with shorter OS (HR = 1.19, 1.05-1.34, p = 0.01), whereas IL-6 (p = 0.25) and CEA (p = 0.26) were not. Patients with elevated serum levels of all 3 biomarkers had the shortest OS (HR = 2.12; 1.29-3.50, p < 0.01). Conclusions: Serum IL-6 and YKL-40 determined before liver resection may be valuable prognostic biomarkers in patients with metastatic CRC.