Although prior research has investigated the link between fibrinogen and mortality risk, there is a notable lack of long-term cohort studies. This study seeks to examine the relationship between plasma fibrinogen levels and all-cause mortality. Fibrinogen levels were divided into low and high groups based on the median and further categorized into quartiles. Kaplan-Meier analysis was employed for survival analysis, and hazard ratios (HRs) were calculated using the Cox proportional hazards model. Our study included 5,690 participants, divided into a lower fibrinogen group (fibrinogen ≤ 370 mg/dL, N = 2,851) and a higher fibrinogen group (fibrinogen > 370 mg/dL, N = 2,839). The survival probability of the lower fibrinogen group was higher than that of the higher group (70.98% vs. 47.98%, P < 0.0001). All-cause mortality was higher in the higher fibrinogen group compared to the low fibrinogen group (HR 1.26, 95% CI 1.09-1.45, P = 0.002). Compared to Q1, mortality risk increased in Q2 (HR 1.26, 95% CI 1.00-1.59, P = 0.05), Q3 (HR 1.39, 95% CI 1.15-1.69, P < 0.001), and Q4 (HR 1.51, 95% CI 1.23-1.87, P < 0.001). Higher fibrinogen levels correlate with an elevated risk of all-cause mortality, suggesting fibrinogen is a potential biomarker for mortality risk.