Inflammation plays a crucial role in prostate cancer (PCa) progression and mortality. This study aimed to investigate the predictive value of the inflammatory burden index (IBI) and its components for mortality risk among men aged 40 years and older. A total of 7,344 participants from the NHANES 2001-2010 were included. High PCa risk was defined as a %fPSA greater than 25% and a tPSA level less than 4.0 ng/mL. Cox regression and logistic regression analyses were conducted to assess the association between IBI, PCa risk, and mortality. Receiver operating characteristic (ROC) curve analysis and random survival forest (RSF) model were utilized to evaluate the predictive value of IBI and its components for mortality. Elevated IBI levels were significantly associated with an increased risk of all-cause mortality (HR = 1.08 [1.05-1.10]) and cancer mortality (HR = 1.11 [1.07-1.15]). High-risk PCa cases also exhibited elevated mortality risk (all-cause: HR = 1.35 [1.19-1.54]; cancer: HR = 1.65 [1.27-2.14]). Additionally, the combined effect of elevated IBI levels and high PCa risk showed a synergistic impact on mortality outcomes (all-cause: HR = 1.49 [1.27-1.74]; cancer: HR = 1.76 [1.29-2.40]). ROC curve analysis revealed that IBI had the highest AUC for predicting all-cause mortality (AUC = 0.690 at 3 years, 0.622 at 5 years, 0.634 at 10 years, and 0.632 at 15 years) compared to its individual components (CRP, NEU, LYM). RSF analysis highlighted IBI as the most significant predictor of all-cause and cancer mortality. The combined effect of elevated IBI levels and high PCa risk demonstrated a synergistic impact on increased mortality risk among men aged 40 years and older. IBI demonstrated superior predictive performance for mortality outcomes compared to individual inflammatory markers. These findings underscore the potential utility of IBI as a prognostic biomarker for mortality risk assessment in individual with high PCa risk.