BACKGROUND Preoperative hyperfibrinogenemia is associated with inflammatory mediators and a poor prognosis in several types of cancer. However, there is no published information on the monitoring of patients with preoperative hyperfibrinogenemia after surgery. The aim of the study reported here was to assess the clinicopathological and prognostic significance of plasma fibrinogen levels in patients with esophageal squamous cell carcinoma before and after surgical treatment. METHODS Plasma fibrinogen levels were analyzed before surgical treatment (endoscopic submucosal dissection and surgery) in 82 patients with esophageal squamous cell carcinoma. The clinicopathological significance of plasma fibrinogen levels and the relationship of plasma fibrinogen levels with several biomarkers were evaluated. The cutoff value for hyperfibrinogenemia was 321 mg/dl. Univariate and multivariate analysis using the Cox proportional hazards model were performed to evaluate the prognostic significance of plasma fibrinogen levels. The changing patterns of plasma fibrinogen were monitored after surgical treatment to evaluate prognostic impact. RESULTS Hyperfibrinogenemia was significantly associated with advanced pathological stage of cancer and high C-reactive protein levels. Plasma fibrinogen levels significantly decreased after surgical treatment in recurrence-free patients but did not decrease in patients with recurrence. The multivariate analysis indicated that preoperative hyperfibrinogenemia was an independent prognostic factor for poor survival (hazard ratio 1.005, 95% confidence interval 1.000-1.010; P = 0.039). CONCLUSIONS Preoperative hyperfibrinogenemia was associated with inflammatory mediators, tumor progression, and poor survival in patients with esophageal squamous cell carcinoma. The absence of a decrease in plasma fibrinogen levels after surgical treatment may indicate the possibility of tumor recurrence.